Golf Science 9781782406440, 1782406441

Table of contents :
Cover
Half Title
Title
Copyright
Dedication
Contents
Introduction
CHAPTER ONE mind and body
CHAPTER TWO the swing
CHAPTER THREE the equipment
CHAPTER FOUR the environment
CHAPTER FIVE coaching with technology
CHAPTER SIX the practice process
CHAPTER SEVEN the score
APPENDICES Notes
Table of measurements
Glossary
Notes on contributors
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Acknowledgements

Citation preview

GOLF SCIENCE

GOLF SCIENCE

Optimum performance from tee to green Consultant editor

Mark F. Smith

This paperback edition published in the UK in 2019 by Ivy Press An imprint of The Quarto Group The Old Brewery, 6 Blundell Street London N7 9BH, United Kingdom T (0)20 7700 6700 F (0)20 7700 8066 www.QuartoKnows.com

Dedication © 2017 Quarto Publishing plc First published in hardback in 2013 All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage-and-retrieval system, without written permission from the copyright holder. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-1-78240-644-0 Digital edition: 978-1-78240-7-096 Softcover edition: 978-1-78240-6-440 This book was conceived, designed and produced by Ivy Press 58 West Street, Brighton BN1 2RA, United Kingdom Creative Director Peter Bridgewater Publisher Jason Hook Editorial Director Caroline Earle Art Director Michael Whitehead Designer Lisa McCormick Commissioning Editor Kate Shanahan Project Editor Rob Yarham 'Science in Action' text Mark F. Smith and Rob Yarham 'Equipment' spread text Mark F. Smith Illustrator Nick Rowland Additional illustrations Alan Osbahr Note from the publisher Information given in this book is not intended to be taken as a replacement for medical advice. Any person with a condition requiring medical attention should consult a qualified medical practitioner or therapist. Cover illustration: Nick Rowland; photo: Getty Images/Phil Leo/Michael Denora Printed in Slovenia by GPS Group 10 9 8 7 6 5 4 3 2 1

This book is dedicated to my beautiful children D & C. ‘The best preparation for tomorrow is just doing your very best today.’

Contents

I Introduction

C HA P T E R O N E

mind

and body

8 12

Mark F. Smith



C HA P T E R T W O

the

swing

38

the

equipment

64

the

environment

90

Paul Glazier and Peter Lamb



C HAPT E R T H R E E

Richard Kempton



C HAP T E R F O U R

Andrew Collinson and Sandy Willmott



C HA P T E R F I V E

coaching

with technology

116

Robert Neal and Mark F. Smith



CHAPTER SIX

the

practice process

134

the

score

160

John Hellström and Mark F. Smith



C HAPT E R S E V E N

Graeme Leslie

APPENDICES Notes Table of measurements

178 184

Glossary Notes on contributors Index Acknowledgements

185 189 190 192

Introduction

Playing golf can be one of the most simple yet perplexing of pastimes. For the millions of players around the world, who challenge themselves each time they pick up a club, golf offers the chance to escape among beautiful scenery, with shimmering green fairways and carefully planted shrubbery and flowers. Golf challenges our mind, as well as body, in ways that can bring elation and despair in the space of a moment. The act of getting a ball in a hole is simply complex when one ponders the number of factors that all interact with the small white spherical object: the golfer, the equipment, the course and the weather. Understanding the science behind golf enhances both the interest in, and the sheer enjoyment of, playing the game. From across the globe Golf Science brings to you leading experts in the physical, mental, technical and tactical aspects of the game. This book binds together their significant findings with those of scientists who have studied almost every aspect of this seemingly simple activity. Some discoveries were made in the nineteenth century and others as recently as this year. A wide range of sciences is embraced in the book because golf involves a surprisingly diverse array of disciplines. The fundamental principles of physics lead to the magic of engineering and technology, which has led to the development of innovative club design, futuristic coaching devices and novel practice approaches. There are the mysteries of biomechanical forces, as well as crucial explanations of aerodynamics. You, the golfer, are also dissected and put under the microscope to reveal how the connection between your mind and body allows you to repetitively execute the complex task of hitting a ball. This is not a manual nor an instruction guide. It goes deeper than such books, but it will help everyone to get more from their golf game – whether picking up a club for the first time, hacking balls down the range,

8

Introduction

a Science behind success

Even a leading Tour pro like Rory McIlroy runs into trouble sometimes. Professional golfers have turned increasingly to science to help them understand every aspect of the game and give them that edge out on the course. Psychology, physiology, nutrition, materials science and physics all play their part in the golfer's quest to maximize their chances of success, even when things don't quite go according to plan.

navigating their way around 18 holes, or competing in tournament play to win. Golf is about the breeze on your brow, watching the ball fly towards the hole, knowing that your swing felt right. Without a doubt, your potential to get it right can be boosted by your knowledge of the science at play.

3

2

1

Scientific discoveries are not always easy to comprehend, but this book presents them in a straightforward way. The Question-and-answer pages contain unique info-graphics that convey scientific results very clearly. Every science question is mirrored by a question posed by a golfer. The text and the info-graphics combine to answer them both. The Equipment pages show how and why crucial elements of the game have helped revolutionize the way we play golf. From early sixteenth-century club-like sticks carved from a single piece of wood to highly sophisticated, scientifically inspired precision tools, golf has embraced the scientific revolution.

a Graphically speaking

The graphics and illustrations in the book will introduce you to the science that has developed over several hundred years of golfing, from the fundamental physics and body biomechanics involved when executing a golf swing to the latest technical developments in golfing equipment.

Spin loft Club direction

10

Introduction

It is all very well explaining the what, why, how and when, but, apart from playing the courses, little can bring a golfer closer to their favourite activity than a world-class photograph. So, the photographic Science in action feature pages reveal how the principle is applicable to the practice, while at the same time conveying the drama, excitement and human endeavour that is golf. For golfers who are eager to delve deeper, there is a comprehensive glossary that defines many of the terms and concepts. An extensive list of references points readers to the sources of the information, so that it is easy to engage more closely with the science.

ntation

Club orie

n

Ball directio

ft

Dynamic lo

Launch angle Attack angle (level or 0˚)

11

Without question the art and science of golf primarily takes place in the mind, played out through the way we move our bodies. This instinctive connection affects how we feel, how we think and then how we swing our golf club. There is no better place to illustrate this than on the course, where our golf can be dramatically affected by what happens in our mind. Tour players have an amazing ability to regulate their thoughts while still allowing their bodies to function at a very high level. How body biomechanics, anatomy, physiology and mental strategies all link together is revealed throughout this chapter. Mark F. Smith explores, through a series of intriguing questions, the science behind the mind–body connection and how it relates to the way the golfer moves and feels, interacting with the equipment and creating movement of the body and ball.

chapter one

mind and body Mark F. Smith

Does physical fitness level affect performance?

Will getting fit improve my game?

From a less-informed perspective, success in golf is often seen to be more about technical, tactical and mental factors than physical ones. Indeed it is true that, historically, physical fitness has not appeared to be of that much importance in golf. Today, however, even some of the ‘old school’ pros are catching on. Miguel Angel Jiménez goes for a jog every morning, and Open champion Darren Clarke has revealed that more time spent working on his fitness has been a key factor in his success. Research proves that good physical attributes – especially stamina, strength, mobility and balance – help to improve golfing performance and lower those scores. Over the short term, walking and golf-related training has been shown to elicit a number of both general health and golf-specific performance improvements. A reduction in body fat helps to maintain a healthy blood pressure and increases functional capacity, both factors associated with the reduced risk of hypokinetic diseases. In other words, undertaking regular

a Healthy body, healthy golf

According to the latest golf science research, technical, tactical, mental and life skills will affect – but will also be influenced by – the physiological status of the player.3,4 Prior to play, the golfer’s objective should be to ensure that their aerobic fitness, strength and conditioning, flexibility, podiatric and optometric performance, dietary habits and injury management are all factored into their overall player plan. Once play begins, the player must then select appropriate strategies, bearing in mind external factors, such as temperature and humidity, in order to maximize their performance – proper nutrition, hydration, clothing, physical preparedness and mental focus.

14

Mind and Body

golfing activities in conjunction with a healthy lifestyle will decrease your chances of developing serious illnesses and will also increase your physical abilities and life expectancy. Evidence also reveals that performing a few simple exercises each day will increase your strength, mobility and balance. Assessing more than 250 players, with a handicap range between 0 and 20, a 2009 research review revealed that playing standard is related to trunk, hip and shoulder strength – the lower the handicap, the stronger the player was in these critical areas.1 Additionally, a number of other studies have identified a link between mobility in the hip, mid-trunk and shoulder with increased club head speed – which means more carry on long shots and greater spin on short shots.2 Studies show that adopting carefully managed physical conditioning routines­– such as flexibility, balance and strength exercises – at least three times per week for 8–10 weeks has a positive effect on club head speed, whatever a golfer’s ability.

Preparation

Diet and nutrition

Aerobic fitness Regular fitness assessment

Mobility, stability and flexibility Podiatry

Strength and conditioning

Optometry

Management of injuries

Shaping up

Physical tiredness impairs mental functioning and impacts on decision-making ability on the course.

Physical fitness builds a player’s immune response, reducing the likelihood of catching colds and coughs.

Maintaining hydration during a round improves concentration, and shot distance and accuracy.

Increasing strength and power in the back, arms and upper legs can improve hitting distance by up to 6%.

Strengthening muscle groups in the lower back and knees stabilizes and strengthens the swing.

Excess body weight places extra strain on the heart, lungs, muscles and joints, reducing performance and increasing tiredness.

a Getting physical

Improving basic health, cardiovascular fitness and core muscle strength through training has been proven to result in better distances off the tee, improved and more consistent technique, and stronger mental focus under pressure.1–5

Improving mobility of ankles, knees, hips and shoulders reduces the probability of injury and improves overall golf performance.

External factors (such as environment)

Competition

Optimum physical state Optimum mental state

Optimum preparatory physical state

Physical maintenance during competition

Competition success: lower score

Optimum technical state Optimum tactical state Optimum life skill state

15

Do ‘quiet eye’ moments help putting success?

Where should I look when making a putt?

Where a golfer looks during the putt may reveal more about what’s happening in the mind during those vital seconds beforehand than was first thought. Scientists from Canada and the United Kingdom have uncovered the role our brain’s visual motor control system may play in enhancing neurological efficiency throughout the stroke.1–4 More importantly, though, they have revealed a solution which helps all players, irrespective of ability, to improve their putting performance.

during the stroke concentrating on the ball and then, once impact has occurred, to continue staring at the same spot on the ground afterwards.

Evidence presented at the 2012 World Scientific Congress of Golf Science reveals that focusing on the ball in a particular way – dubbed ‘quiet eye’ moments – eliminates unwanted distractions, and leads to more successful putting. Based on a number of controlled experimental studies, it has been suggested that the key is to spend around two seconds

It is thought that this approach is effective because it allows the golfer to take in only the necessary visual information required to make the shot. Focusing away from the intended task at hand can disrupt the functioning of millions of neurons in the brain that convert the visual information into movements of the putter. Given that putting is a hugely important part of golf, accounting for around 45 per cent of the shots taken in an average round, researchers are beginning to acknowledge that this approach may be vital to success, improving both precision and accuracy, and preventing the breakdown of the movement under high levels of pressure and nerves.

d ‘Quiet eye’ study Golfers were monitored on a follow-up trial and another performed under pressure. Those who undertook ‘quiet eye’ training showed marked increases in the time spent fixating on the target line and location of the ball, and, more importantly, the percentage of putts holed from 3 m (10 ft) improved.

d Putt it there By adopting their stance, then gazing calmly and steadily at the hole, bringing the eyes back to the ball and then fixating on the back of the ball, the golfer should be able to get their longer putts much closer, avoiding those embarrassing three-putt moments.

QE period (QE trained) QE period (control) % holed (QE trained) % holed (control) 1 cm = approx 0.4 in

Study results 12

90

11

70

2000

60 50

1600

40

1200

30

800

20

400

16

Mind and Body

Pressure test

Performance error (cm)

2400

Retention test

Performance error (control)

1 cm = approx 0.4 in

10

Holed (%)

Mean QE period (ms)

100

80

Pre test

Performance error (QE trained)



Putting performance

2800

0



9 8 7 6 5 4 3 2

10

1

0

0

Pre test

Retention test

Pressure test

Eyes on the prize Highly skilled golfer

Less-skilled golfer

As a player’s skill level improves, their ability to fixate on a specific location on the ball increases, both during the backstroke and through impact.

Players with a lower putting ability tend to scatter their gaze, rather than select a specific location on the ball.

The player’s focus is more defined, with the hole becoming a single target.

The good putter generates a more precise scanning path between the ball and its target.

Gaze is unpredictable for the poorer putter, with no clear scanning path identified.

o On the ball

Analysing a golfer during the final moments of a putt has revealed what may be two key indicators of putting success: where the player fixes their gaze prior to making the backswing; and how long they stare at a particular location on the ball. In a series of studies investigators found that highly skilled golfers

focused on a precise point on the ball and target line.1–3 It is thought that the brain’s neural networks are able to initiate a good putt during these ‘quiet eye’ moments, while overriding competing neural processes responsible for generating distractions and anxiety.

g Quiet time Putting accuracy 32.0

75

31.5

73 71

30.5

69

30.0 29.5

67

29.0

65

28.5

63

28.0

61

27.5 27.0 26.5 Pre training

Post training

2–3 m putts holed (%)

Mean putts per round

31.0

26.0

The fixation area is less well defined in the less-skilled golfer. More erratic scanning of the area results in no clear target.

‘Quiet eye’ training seems to improve putting scores during competitive on-course play .[2] Performance data collected over a number of competitive rounds before and after training revealed that players who embarked on a regular training regime reduced their number of putts per round by an average of 1.92 shots, holing out 5 per cent more putts from 2–3 m (6–10 ft). Interestingly, when compared to US PGA 2011 Tour putting statistics, if a golfer ranked last (186th) experienced an improvement of 1.92 putts per round, they would climb 139 places to 47th in the rankings.

59

% 6–10 ft holed (QE trained)

57

% 6–10 ft holed (control)

55

Need to know The ‘quiet eye’ technique: • Line up a shot, alternating with quick fixations between ball and hole. • Before and during the stroke, hold a steady fixation on the back of the ball, for around 2–3 seconds. • After contact with the ball, keep the eyes steady for a further half a second.

Putts per round (QE trained) Putts per round (control)

17

Does ageing impact on golf performance?

As a senior, does golf improve or damage my health?

An inevitable part of life is the fact that we all grow old. How our bodies age is a hotly disputed topic among gerontologists (the scientists who study the ageing process). Some suggest that ageing is largely the consequence of a series of random events, experienced through our interaction with the environment, altering and eventually damaging our molecular make-up. Others conclude that random events alone are not sufficient to explain all ageing processes. They believe that ageing is more a matter of destiny and that our lifespans are in part pre-programmed even before our births. Whatever the complex mix of genetic, environmental, lifestyle and socioeconomic factors influencing the lifelong process, we can be certain that ageing results in a progressive loss of physical and mental function.1 It’s not all bad news for the ageing golfer. Despite many of the age-related changes affecting older players’ risk profiles, playing golf regularly offers ways of preserving flexibility, strength, endurance, muscular speed, balance and cognitive function.2,3 Playing golf doesn’t require high levels of physical

fitness, which is one possible reason for its popularity among older individuals. However, the golf swing is a complex movement pattern that puts various joints of the body under stress, and golf participation has been shown to be responsible for injuries to the lower back, wrist, elbow and other joints of the older golfer, which can also lead to a high risk of injury recurrence.2 Because of this, the importance of proper conditioning for the senior golfer should not be underestimated. Continued participation in golf can be a very important form of exercise and social interaction for an older adult. Furthermore, research reviews2,4 conclude that conditioning programmes, in addition to regular rounds of golf, are highly recommended for all older players irrespective of their level of participation. Not only could the programmes prevent injury, they also have the potential to improve performance. Such programmes do not need to be elaborate – home-based exercises incorporating one’s own body weight, weighted clubs or elastic tubing resistance are very effective.

Increase in club head speed 134.5 (83.5)

a Driving improvement

What is clear is that for the ageing golfer regular physical activity, such as a round of golf twice a week, improves musculoskeletal, cardiovascular and cognitive function.1–3 Evidence reveals that three 90-minute golf-specific exercise classes per week for eight weeks – in addition to playing – improve golf performance.4 For a group of senior golfers, with an average age of 71 years, regular exercises that developed their functional ability – balance, stability and mobility – resulted in an average improvement of 6.3 km/h (4 mph) in driver swing speed. Converting this to distance, given a calm day, would mean an extra 10–15 m (11–16 yards) of carry distance off the tee, and probably more roll distance as well.

Control group 127.3 (79.1)

Exercise group 133.6 (83.9) 115 (71)

120 (75)

Mind and Body

125 (78)

130 (81)

135 (84)

Average club head speed km/h (mph) Pre test

18

133.3 (82.7)

Post test

140 (87)

Staying healthy

Lungs As we get older, the elasticity of our chest wall and lung tissue decreases, so we can’t move air into and out of our lungs so efficiently. This means that, during physical activity, our breathing can’t respond so well to provide the additional oxygen our tissues need, resulting in breathlessness. Regular exercise helps to improve and maintain lung function, so both the rate of breathing and the volume of air inhaled and exhaled in each breath increase more efficiently during exertion, and the sense of breathlessness is reduced. Nervous system The functioning of our nervous system declines with age. Nerve endings in the muscles, called proprioceptors, that send sensory information to the brain about the positioning of different parts of the body become less efficient, and the conduction velocity of electrical impulses along nerve axons slows. With regular activity older adults can help preserve neural function, and so maintain reaction times, balance, stability and postural co-ordination. Fat deposits A more sedentary ageing lifestyle can lead to increased prevalence of abdominal fat deposition, with elevation in overall body fat and associated reductions in fat-free mass. Effects can include impaired mobility, increased risk of lower back pain and greater threat of hypokinetic diseases. If an older person maintains an active lifestyle, however, these risks are greatly reduced. Connective tissue In older adults, connective tissue can become more stiff, brittle and weak, with increased risk of tendon and ligament injury. It also has a decreased ability to return to its original length when injured, affecting stress properties. Physical activity is known to increase collagen turnover in connective tissue, which gives it improved pliability.

Brain Cognitive decline is an inevitable consequence of the ageing process,1 affecting abilities such as memory, reasoning and problem-solving. Long-term involvement in cognitively challenging activities, like playing golf, can result in changes to brain structure and function,5,6 having a positive effect on cognitive activities.

Heart Maximal aerobic function declines by appropriately 7% per decade from the age of 20, with cardiac function, expressed as maximal heart rate, decreasing by 4% per decade.7 For the ageing golfer, regular physical activity can maintain, and even improve, aerobic function.

Muscles (arm) Depending on training and inherited traits, maximal muscle strength declines by an average of 1.5% per year after the age of 60, with the cross-sectional area of the muscle declining by 10% per decade after 50.8 Maintaining physical activity levels plays a key role in preserving muscle mass and overall strength. Bone mass Age-related declines in body mineral content, overall bone mass, cartilage water content and joint lubrication increase vulnerability to injury and mechanical dysfunction. The gravitational loading and muscular traction that occur when walking around a course improve bone thickness, strength and calcium concentration.

g Peak condition

Golf presents both potential health benefits 2 and risks 3 for the senior player. The risks, such as musculoskeletal strains or cardiovascular stress, are compounded by the fact that the systems of older players may not be as efficient at withstanding the demands of this type of repetitive exercise. Research 2–4 has concluded that conditioning programmes for the senior golfer are highly recommended, substantially improving health and golfing performance.

19

Does a balanced posture affect putting success?

How should I stand when putting?

Despite the relatively small body movements involved during the putting stroke, how a player stands and moves during those few brief seconds may reveal how posture at address and through the stroke could play a more important role than first thought in determining putting success. Top players look to create a stable, balanced and solid base, along with a fixed pivot point to execute the stroke consistently.1,2 Without these, the putting stroke may not stand up under pressure. Using the latest scanning technology, a study published in the Annual Review of Golf Coaching1 measured the pressure under the feet of right-handed amateur and professional golfers while addressing the ball and making a strike. Recordings of the weight distribution between the right and left foot and the toes and heels revealed that amateurs place on average 20 per cent more weight on the right side than on the left, with more pressure through their toes than heels. Professional players have a more even distribution, spreading pressure more consistently. When measuring the movement of pressure throughout the putt, the study also identified that amateur players created more sway during the putt, while the professionals remained relatively still. With uneven weight distribution at address, the researchers suggested that the amateur player is already placing their body in an ‘unbalanced’ posture before they attempt the putt, meaning that any subsequent movements will simply be compensating. It has been found that many right-handed amateurs place a greater percentage of pressure on the right foot than on the left, and more towards the right toe (vice versa for left-handed players) when standing still. When in the putting address posture the same pattern is observed; golfers with handicaps greater than 10 performed significantly worse than those with handicaps less than zero when both were asked to balance on one foot.2 Given the importance of postural stability before and during the putting stroke, using activities that improve balance can lead to a more repeatable and mechanically sound ball strike. 20

Mind and Body

A good The right balance putting technique creates a stable posture and pivot Amateur Professional point to allow the putter 21.00% 32.43% 26.97% 27.48% to be returned consistently from address to impact without adjustment. Research suggests that variations in balance at address, and in the extent of pressure movement 19.40% 27.17% 21.37% 24.18% during the swing, may account for differences Mean area pressure values for in putting success different right-handed players between amateurs and professionals. Pressure shift for amateur players

a Footwork

Start to top backswing

Top backswing to impact

17.6 mm (0.7 in)

12.2 mm (0.5 in)

Impact to finish

53.3 mm (2.1 in)

Mean pressure centre shift Pressure shift for professional players Start to top backswing

Top backswing to impact

Impact to finish

12.2 mm (0.5 in)

10.1 mm (0.4 in)

42.0 mm (1. 7 in)

Mean pressure centre shift

Pressure putting The inner ears house the vestibular system, which monitors the directions of motion, such as moving forwardsbackwards from toe to heel, or side-to-side from right to left.

The central nervous system, comprising the brain and spinal cord, processes the information received from the sense organs, co-ordinating the body.

The eyes observe where the body is in space and also the directions of motion.

Monitor display

Mechanoreceptors, positioned within muscles and joints, report which parts of the body are moving and where tension resides.

Pressure receptors located under the skin in the feet sense the distribution of pressure touching the ground.

o Analysing balance

This illustrates a typical pressure image of a right-handed amateur golfer at the address position for a putt. The pale pink, dark pink, and red colours show the depth of pressure. For this amateur, as for many, the distribution of pressure is greater on the right foot and on the toes. Research1 indicates that on average 60 per cent is on the right foot and 40 per cent on the left. Professional tournament players have a much more even distribution of pressure across left and right and heel and toe for putting (50 per cent split).1 Having an unequal balance before starting the stroke will certainly impact on the balance throughout the swing, and it is likely that this will begin unwanted movements to keep the club on line through impact.

Putting stance on pressure-sensing mat

o Putting posture

An important component of the complete golf swing, good posture at the start and throughout the movement reflects good balance, stability and mobility. Research shows that golfers with poor postural balance at address may lose rhythm or tempo, which affects their mechanical efficiency.1

21

Does golf performance relate to perceived hole size?

Can imagining a bigger hole help me play better?

The history books reveal conflicting stories as to how the size of the hole was originally determined. Some sources suggest the hole size became standardized when golf officials began using a common drainage pipe to produce the hole. There is also reliable evidence that in 1829 officials at the Royal Musselburgh Golf Club in Scotland invented the first known hole-cutter. It produced a hole 10.8 cm (4.25 in) wide. From this point on, all holes on every course were standardized. However, even though actual hole size remains constant on modern courses, players’ perceptions of dimensions on the green may vary considerably. A growing body of research demonstrates that how well the golfer is performing may actually affect how they perceive the size of a hole and distance to the pin. Evidence from the sport of softball has shown that players who are hitting well perceive the ball to be bigger than players who have more difficulty hitting.1 Also, research shows that when study participants were asked to reach for a target with and without a tool (for example, a golf club), despite targets being presented at the same distances, perceived distances to targets within reach with the tool were compressed compared with those to targets that were beyond reach without it.2 In another series of studies, golfers who played better, having lower scores on the course on that day, judged the size of a hole to be bigger than players who played worse,

having higher scores.3 However, handicap, which is a measure of longer-term playing ability, did not significantly correlate with the judged hole size. Combined, these results suggest that better players did not see the hole as being bigger, but players were playing better on that given day did. In a further experiment, players with a short putt of 0.4 m (1.3 ft) perceived the hole to be bigger than golfers with a longer 2.1 m (7 ft) putt. The results suggest that when players are faced with a shorter test they perceive the hole to be bigger, and success therefore more likely, than golfers facing a longer, more difficult putt. Since putting is harder from a further distance and performance was markedly worse in the longer putt task relative to the shorter putt, these findings suggest that putting performance influences apparent hole size. These studies suggest that a relationship exists between golf performance and perception of hole size, but the causal direction of the findings remains unclear. Do golfers putt better and therefore see the hole as bigger, or do they see the hole as bigger and therefore putt better? The research does not answer these questions, but it can be speculated that the relationship is reciprocal so that a golfer’s perception of hole size and their putting performance are likely to influence each other.

Sizing up the hole

a Optical illusion

More than any other aspect of golf, putting relies on one’s eye – how one reads the undulating greens and finds the true path to the hole – and perception. To assess how the perception of the hole may both influence and reflect one’s psychological state, Witt and colleagues’ research recreated a well-known illusion: the smaller circles around the golf hole make the hole appear bigger than it really is, while the larger circles make the golf hole look smaller. This distortion of reality – called the Ebbinghaus illusion – has been well documented, and the researchers confirmed that the

golfers’ perceptions were indeed distorted as predicted.4

22

Mind and Body

Size is everything

g Perception against performance

Evidence reveals that how a player perceives the size of a golf hole is a function of score on the course that day. In one such study3 researchers asked players, once they’d finished their round, to select a hole size that best corresponded with the actual size of a golf hole (10.8 cm/4.25 in). With hole size increasing by a non-uniform diameter, a significant negative relationship (red line) was found between course score and the circle selected as best matching the actual size of the golf hole. Demonstrating that a golfer’s perception of hole size is scaled by their current abilities, golfers who are playing better see the hole as bigger than do golfers who are not playing as well.

13 cm 5 in 12.5 cm 4.92 in

Perceived hole size

12 cm 4.72 in 11.5 cm 4.53 in 11 cm 4.33 in 10.5 cm 4.13 in 10 cm 3.94 in 9.5 cm 3.74 in 9 cm 3.5 in

60 80 100 120 140 Course score

Mind the hole

g Believing is seeing

Research indicates that the perception of the spatial layout of a golf hole may be not only a function of optical information about the cup, but also a function of the golfer’s perception of their own immediate performance. In a series of experiments, scientists demonstrated that golfers perceive the size of a hole relative to their current golfing performance. In other words, players who played better, or putted closer to the cup, judged the hole to be bigger.

23

equipment: golf shoe

The outcome of a golf swing is dependent upon precision, balance and consistency. Every great swing has a starting point or setup, which places the golfer in an optimal position to execute a repeatable, efficient golf swing and ball impact. To generate the athletic movement of the swing, the relatively relaxed and stable posture must start from the ground up. After all, it is the interface between the ground and the foot that creates the stabilization upon which the swing movement can build and develop. During the initiation of the movement, the body builds muscular tension from the ground up, through the connection of the lower and then upper body segments, triggering the start of the backswing.

0291-0091 1920s

To ensure a stable platform for the initial accelerating physical forces of the swing, the golfer’s connection with the ground needs to be optimized and, to this end, the modern golf shoe has evolved from humble origins about 150 years ago, as merely a boot with nails in the sole, into a high-tech golfing tool – more like an athlete’s shoe.1,2 Engineered to assist the player in making the push-off needed on power shots, the latest innovative designs allow the shoe to bend and twist while offering ample ground-hugging traction that helps stabilize the feet during powerful shots requiring significant leg push.

1940s 1940 Ladies alternative style

1950s Ladies 1940’s

1950’s ladies 1960s

1856

1891

1906

1917

1923

1940

The earliest reference to spiked golf shoes appears in an issue of The Golfer’s Manual. In this Scottish publication, novice golfers are advised to wear stout shoes ‘roughed with small nails or sprigs’ to walk safely over slippery ground.

To provide more stability to the golfer, screw-in spikes were introduced. While they were more comfortable than the hob-nail shoes and boots worn by some golfers, during the next century groundskeepers complained about the spikes damaging the greens.

The first standard-looking golf shoe was introduced, which offered the golfer an extra saddle-shaped piece of leather around the laces. Named Saddle Oxfords, these were originally designed for racquet sports, but gained more popularity among the golfing fraternity.

The first US patent was granted to William Park for his then ‘innovative’ golf shoe design, which was more of a boot than a shoe! The materials used at this time were leather, wood and canvas.

By the early twentieth century, the golf boot had turned into the golf shoe when the Field and Flint Company decided to improve men’s golfing footwear.

It was during this year that women’s shoes were first introduced in America. During these times the shoes looked like men’s shoes.

24

Mind and Body

Today’s shoe

Incorporating a gel-based foot-bed with a reinforced heel support system, the modern shoe is both comfortable and functional, preventing unwanted movement and giving a firmer hold.

Upper sole components of the shoe, which surround and bolster the foot, are strategically located to promote more lateral stability of the foot.

Decoupling grooves are incorporated within the sole to allow specific zones to move freely, keeping the foot more balanced and stable throughout the swing.

Innovation in the lacing system ensures the foot is kept stable and firm as forces act on it throughout the swing.

The evolution of the spike now offers superior traction and greater stability throughout all positions of the golf swing.

Thinner, more durable materials reduce heat retention, resulting in less fatigue during the round.

Optimized cushioning and improved energy return are provided by optimally placed shock absorption units throughout the sole.

Lower-profile outsole technology attempts to bring the foot even closer to the ground, offering improved stability, balance and feel.

a Stepping up

Golf shoes serve as a functional high-tech piece of equipment, offered with a variety of materials, soles and cleats. The traction, flexion, moisture control and comfort of golf shoes have been designed and engineered to deliver a state-of-the-art golfing tool. 1970s Advancements in manufacturing techniques and shoe design saw the first rubber-soled golf shoe appear on the market. This reduced shoe weight and improved balance and stability.

The latest footwear is now built on a wider footplate, providing larger contact areas between shoe and turf. It’s been suggested that this improves balance and stability by increasing connectivity throughout the swing.1,2

A reinforced toecap not only offers durability, but may also act to reduce front foot compression loads during the follow-through.

1980s

1990s

1995

2010

Waterproof-treated leather started to appear as a material of choice among major manufacturers. The shoe also started to become more athletic looking, resembling a sports shoe, focused on foot support and comfort.

The introduction of non-metal cleats on golf shoes gained popularity, offering better traction during the swing and causing less damage to the golf course.

More advanced materials offered more breathable yet fully waterproof uppers.

Golf shoe technology and design started to mimic advanced athletics shoes, allowing for a more natural motion of the foot, a substantial reduction in weight, and lower-profile soles to improve balance and stability.

25

What does ‘functionally connected’ mean?

Why are mobility and stability important?

Many coaches regard staying ‘connected’ throughout a golf swing as maintaining a tight relationship between the body, arms and club from start to finish. More scientifically, the concept of connectedness has both a mental and a physical dimension. From a psychological stance, being internally connected could be viewed as having an inner calmness, being present in the moment, and being relaxed and ready. Conversely, a state of disconnectedness is associated with anxiety, feelings of negativity, or self-doubt.1

From a biomechanical perspective, the notion of a connected swing can signify that all body segments are either accelerating or decelerating in the correct sequence with precise and specific timing so that the club arrives at impact accurately and with maximum speed.2 Additionally, efficient connectivity between the body’s neural pathways ensures communication between regions of the brain responsible for processes such as motor planning, control, estimation, prediction and learning.3

Mobile joints (blue) and stable segments (red) Cervical spine/neck Gleno-humeral/shoulders Thoracic spine Elbows

Hips Wrists

Knees

Ankles Feet

26

Mind and Body

Pelvis/sacrum/lumbar Mobility Mobility allows the body to move in all six degrees of freedom to perform any action without having to sacrifice stability. Mobility allows for the generation of elastic energy between muscles, and establishes a base for efficient power production. Stability Keeping one part of the body secure (stable) while stretching and contracting adjacent segments allows the golfer to generate speed and maintain a consistent posture throughout the swing.

More broadly speaking, connectedness can refer to the ability to complete the desired pattern of movement, activating and steadying the correct body segments.4 In turn, this will produce a consistent, powerful and synchronized series of muscular activation patterns necessary for an efficient movement. If this series is altered, through poor technique, inflexibility or muscular weaknesses, dysfunction will occur and the body will try to compensate, creating new and inconsistent body movements. So, from a physiological point of view, golfers need to ensure their body performs two important activities to stay functionally connected throughout

their swing – effective regional mobility and stability. Mobility refers to the combination of muscle flexibility and joint range of motion, while stability is the ability to control the motion of a joint. During the golf swing, the body is an alternating pattern of stable segments and mobile joints. If there is a limitation in the mobility of a mobile joint, the stable region above or below will compensate to create movement and the stable segment will become mobile. When this sequence of muscle events is affected, the golfer becomes functionally disconnected, and the physical sequencing of the swing changes, in turn changing the swing’s consistency, power and accuracy.2

d Mobility versus stability In order to create an efficient action, the body must operate in an alternating pattern of mobile joints and stable body segments. If this sequence is altered, dysfunction in movement patterns will occur. For the golf swing, this means that upsetting the combination of mobility and stability will adversely affect the execution of the swing, the body speed and transfer of this speed to the golf club.

Wrists

Active mobile joints (blue) and stable segments (red) during the swing Cervical spine/neck

Gleno-humeral/ shoulders

Thoracic spine Elbows Pelvis/sacrum/ lumbar

Hips

Knees

Hips Wrists

Knees

Ankles

27

What can we learn from the brain activation patterns of top players?

What happens in the brain during the pre-shot routine?

Successful golfers have the canny ability to refocus after unwanted distractions, have control over their thoughts and emotions, and employ cognitive techniques in imagining intended shot outcomes. In addition to these characteristics, top performers can also deploy consistent cognitivebehavioural strategies that are maintained throughout competition. One specific cognitive-behavioural approach used in golf is the pre-shot routine. This ritualistic sequence of events that, time after time, prepares the golfer for their shot, is a process of mental and physical rehearsal. What a golfer thinks during these vital seconds before the swing may begin to reveal what is actually happening in the brains of the top players. By using functional magnetic resonance imaging techniques, otherwise known as fMRI, scientists from across the globe are beginning to observe fairly striking differences in the brain activation patterns of players during those all-important seconds before the shot.1–4 By examining the neural events in the brains of golfers while they are visualizing their normal golf swing,2 or performing their mental pre-shot ritual,3 researchers

have begun to show that during these periods of mental rehearsal there is less neural activity in the brains of better players. At the lower-skill level, the typical swing is a complicated array of moves and adjustments, errors and corrections, anticipation and worry. Simply trying to organize thoughts and plan movements ahead of the strike can result in intense brain activity. With diminished brain activation occurring as skill level increases, it has been concluded that as a consequence of practice and experience, the tour player’s brain becomes less activated during these periods as their movement creation and shot planning becomes more automatic.

d Thought cycle Neuroimaging research has uncovered differences in the brain activation patterns of professional and amateur golfers while undertaking their normal pre-shot ritual.2 Brain scans have revealed that areas of the inner brain, linked to functions such as emotional control, working memory and topographical recall, seem more activated in amateurs than in professionals. It is thought that lower-skilled golfers – with less natural and automated movement patterns than professional golfers – make more conscious choices, allow distractions to flood the mind, and are unable to eliminate unwanted emotional thought. This in turn fires higher levels of brain activation.

Control centre Amateur golfer

Professional golfer The supplementary motor region is associated with the generation of movements, movements requiring the use of both hands, and planning movement sequences.

The limbic regions of the brain are associated with functions that include emotion, behaviour, motivation and memory.

28

Mind and Body

Preparing for the shot Primary motor cortex Supplementary motor area Inferior posterior parietal cortex

Premotor cortex

Frontal lobe

Although they represent very early stages of neuroscientific exploration inside the golfer’s brain, these findings may just start to open a window into the inner workings of great players’ minds. There still remain many unanswered questions, however. Would different fMRI patterns be seen in association with different clubs? Does the activation vary if the golfer imagines hitting over a huge hazard versus hitting down a broad, expansive fairway? Can this technique be used to improve play? Emerging neuroscience research may soon provide answers.

o Pre-shot process So what may be happening in the brain of a Tour player when preparing to make that all-important shot? The creation of the golf swing movement during the pre-shot phase occurs within the premotor cortex, which prepares commands for voluntary actions triggered by the environmental context (such as distance to target, ground conditions, wind speed). The supplementary motor area prepares commands for internally generated ‘intentional’ actions, which are then executed by the primary motor cortex. Signals containing copies of prepared motor commands (i.e. the swing) are also sent to the parietal cortex, where they are used to predict the sensory consequences of movement – in other words, to provide a mental picture of what the swing and shot outcome may look and feel like. 29

Will I get a bad back from playing golf?

The golf swing may appear to be relatively low-impact, given that the golfer remains in contact with the ground at all times, isn’t hit by anything, and doesn’t hit anything large. However, the explosive twisting, pulling, pushing, compressing and bending motion during the swing causes considerable stress, particularly on the spine, which must withstand rotational loads caused when the upper body twists around the lower body. This is known as thorax–pelvis separation or the ‘X-factor stretch’ (see pages 44–45), which occurs at the top of the backswing and the start of the downswing. The average recreational player, who is likely to play twice a week, swings the club nearly 20,000 times per year – can the body handle the mechanical loads placed on it when repeating this dynamic and explosive movement?

These problems may include muscle strains, slipped disc or stress fractures of the vertebral body.2 Most injuries of the back are cumulative – known as ‘cumulative trauma disorders’ (CTDs).8 A player who is out of shape, has poor address posture, or lacks mobility in the hips, mid-back and shoulders, may eventually injure their back. The best way to improve your swing efficiency is to seek expert advice from a professional coach, who will also be able to advise on exercises to improve your mobility, flexibility, stability and strength. 30

Mind and Body

Spine

Spine

8

Shoulder

Elbow

61 57

5

Shoulder

6

8

Wrist/hand 10

6

Knee

Ankle/foot

1

8

Amateur 5,6,8

Hip/groin

With the swing lasting little more than a second, and generating a club head speed of nearly 160 km/h (100 mph), the back has been calculated to produce compression loads in excess of 7000 newtons;2 this means that for a 80 kg (175 lb) golfer there is the equivalent of around 10 times their own body weight acting on their spine. The back has evolved anatomically to provide reinforcement during compression, lateral bending, and torsion of the spinal discs to withstand these stresses during movement. However, amateur golfers can generate around 80 per cent greater torque and shear loads than professional golfers because of an inefficient swing, thus leaving the weekend golfer prone to back problems.2–4

Percentage of muscle injuries

Hip/groin

What are the main mechanical stresses on the body during golf?

4

13

Elbow

7 Wrist/hand

Knee

6

Ankle/foot

Professional 1,7,8

Twist and swing

The cervical or neck region of the spine consists of seven vertebrae, known as C1 to C7. The top cervical vertebra is connected to the base of the skull. The thoracic region of the spine is located at the chest level, between the cervical and lumbar vertebrae. The 12 thoracic vertebrae, known as T1 to T12, also serve as attachments for the rib cage. The lumbar region of the spine is located between the thoracic vertebrae and the sacrum. The five lumbar vertebrae, known as L1 to L5, are the main weight-bearing section of the spinal column.

Sacrum

Lumbar spine

o Lumbar loading

The lumbar’s key role during the rotational movement of the swing is stabilization. Only marginal rotation – between 2 and 3 degrees of intersegmental twist – may be enough to cause the onset of micro-trauma. Torsional loading of the lumbar spine during the swing, often caused by poor hip or mid-back mobility, can lead to acute local soft-tissue damage, such as muscle strain or internal disc disruption.2–4

o Torque talk The twisting force that occurs in the lumbar region during the swing may cause injury over time, if the golfer has not prepared and exercised adequately.

g Spine-crunching

It is agreed by many experts that changes in the golf swing over time – to emphasize swing speed and ball distance – have led to an exaggerated lateral bending or ‘spinal crunching’ within the lower regions of players’ backs (the backward ‘C’ shape of the spine). As the ‘X-factor stretch’ has increased to generate greater rotational forces, greater loads are placed on the lower spinal column and supporting muscular structures.

31

SCIENCE

IN ACTION

remaining calm and confident

Anyone who plays golf regularly knows that learning on the driving range is one thing, putting all that into practice effectively and consistently on the course is something else. Maintaining a state of calm before, during and after each shot, and retaining confidence throughout the round, are as crucial to a low score as a player’s skill level. No matter how skilled the player, a slip of concentration, a loss of focus, or dwelling on poor shots, all provide a recipe for disaster, but the physical state of a player also contributes to their mental state. Combining physical and mental discipline has been proven to help a player maintain their levels of concentration and so improve their performance on the course. Good levels of physical fitness are the starting point for a winning mental strategy. Staying alert throughout all 18 holes requires stamina, and stronger muscles reduce the strain and tension a player may experience during each shot. Physical fatigue will begin to reduce the effectiveness of the body and the brain later in the round. This also means that a player needs to take on the right levels of nutrition and fluids to maintain physical performance and mental acuity. Leading players also learn to control their breathing and their heart rate before and during a shot. This helps their muscles to relax and execute the movements that they’ve been trained to perform during practice. Tour pros also use various techniques, such as the pre-shot and ‘quiet-eye’ routines, to reduce the neural activity in their brains, eliminate distractions, reduce cognitive anxiety and help them focus on making the shot. A number of studies1,2 have indicated that the level of cognitive anxiety – in other words, doubts about performance before and during play – is less important to actual performance than the direction of that anxiety, that is, whether the player uses that anxiety to be ultimately helpful to themselves.

32

Mind and Body

a Staying in the present The course is full of hazards waiting to penalize any golfer for wayward shots. Keeping calm and composed, even when your game plan falters, requires confidence, focus and control of negative emotions. Having placed his tee shot into the water, Tiger Woods stays calm and takes a drop on the par-3 15th during his first round of the 93rd PGA Championships.

33

Do hydration levels affect mental and physical performance?

Will drinking water regularly help my score?

Playing golf – particularly in warm weather – leads to sweat loss and dehydration, and this can have an impact on both mental and physical functions during recreational and competitive play. Dehydration has been shown to reduce motor performance, cognitive function and alertness in a range of athletic and non-athletic groups. Research using cognitive-motor tasks to measure perceptual discrimination, target accuracy, visual tracking, choice reaction time, attentional focus, concentration and fatigue perception has concluded that the effects of mild dehydration – of 1–3 per cent ΔBM (change in body mass) – result in cognitive-motor dysfunction. Whether such mild dehydration impairs neurophysiological function during golf-specific cognitive-motor performance has yet to be fully explored, but new research has started to reveal that not replenishing lost fluids while out on a course can actually result in an increase in the number of errors a player makes, affecting their score. Findings from a recent study published in the Journal of Strength and Conditioning Research support previous suggestions that mild dehydration – a reduction of around 1–2 per cent in body mass – significantly impairs mental and physical function during golf.3 This study was the first to show that mild dehydration can adversely affect hitting distance, accuracy and judgement of distance during play. The results demonstrated that even a small reduction in body mass,

a Water

As the single largest component of the human body, water accounts for around 60 per cent of the total body mass. For a healthy golfer with a body mass of around 70 kg (155 lb), that makes up about 42 litres (11 gallons). The performance of prolonged exercise, like golf, particularly in warm environments, can result in a substantial loss of body water, with the potential for adverse effects on performance capacity.

34

Mind and Body

attributed to acute mild dehydration (a mean of –1.5 per cent ΔBM), augmented by an absence of fluid intake for 12 hours, impairs golf performance. Given that players are on-course for periods of around four hours, often with limited opportunities to take on fluids, maintaining hydration levels throughout a round can be compromised. Currently, researchers still acknowledge that there is no consensus as to whether reduced cognitive-motor function, increased by mild dehydration, is a consequence of physiological homeostatic imbalance – such as hormonal or cellular effects resulting from dehydration – or caused by central motor behaviour changes attributable to increased sensations, such as thirst. New evidence appears to indicate that impaired cognitive-motor performance may actually be linked to a centrally mediated mechanism of thirst perception, rather than to a loss of total body water. In other words, a signalling mechanism in the body may promote a greater conscious perception of effort in order to encourage a change in behaviour.

Water as percentage of body mass Protein 16–18%

Protein 14–16%

Mineral 5.8–6.0%

Mineral 5.5–6.0%

Fat 15–20%

Fat 20–30%

Water 55–65%

Water 55–65%

Effects of dehydration Physical performance

Mental performance 1 Mental tiredness will increase and both alertness and concentration will be reduced.1,4

1

2 Golf skill and accuracy will be affected, with reduced co-ordination meaning the player will hit the target less often and with poorer precision.3

4 Cardiovascular and central nervous systems will be affected, causing increase in heart rate, lower blood pressure and loss of muscle strength. 5 Physical fatigue will result in loss of co-ordination, balance and stability, affecting shot accuracy and distance, and movements will appear to require more effort.2,3

4

3 Decision-making will be impaired, impacting club and shot choice as well as judgement of distance.3

2 5

6 Even a small reduction in body mass resulting from dehydration can reduce muscular strength by up to 6%.1

6

a Water shortage

According to the latest research, mild dehydration can affect mood, energy levels, and the ability to think clearly. Hydration experts say that our thirst sensation doesn’t usually appear until there has been a reduction of 1–2 per cent in body mass, when dehydration has already occurred. By this stage, both our mental and physical performance may have already felt the impact. 3

Consequences of water loss Hydration as percentage of body mass

100

g Go with the flow

98 96 94 92 90

Optimum performance

Reduced aerobic endurance, reduced mental capacity

Reduced muscular endurance

Reduced muscle strength/ Heat endurance heat cramps exhaustion, fatigue

Physical exhaustion, heatstroke, coma

A 91 kg (200 lb) player would only have to lose on average 1.4 kg or 3 lb (–1.5 per cent ΔBM) – that is, 350 ml (12 oz) of fluid depletion per hour during a four-hour round of golf – to impact on mental and physical performance during the final, often crucial, holes. With possible sweat rates in temperate conditions (18–22ºC or 64–72ºF) of around 400 ml (13.5 oz) per hour when walking at around 5 km/h (3 mph)1 a player must maintain fluid replacement during a round.

35

Does cardiorespiratory response affect putting?

Should I breathe in or out to hole a putt?

It is a long-held belief, pioneered in the early 1970s by Professor Herbert Benson, that a relationship exists between the control of the body’s physiology and the functioning of the mind during moments of stress. For a golfer under pressure, when the game is on a knife’s edge, being able to regulate bodily responses by focusing attention in particular ways could mean the difference between holing that game-winning putt, or missing it. In 2009, researchers from Australia stumbled across a theory known as the intake-rejection hypothesis that may in part explain why successful golfers are more likely to sink more game-winning putts than novice players.1 Exploring the relationship between playing ability and key physiological responses during the putting stroke, it was found that those who were most successful at sinking an 2.4 m (8 ft) putt tended to demonstrate different cardiac and respiratory responses before and during the stroke. Within the complex neuro-circuitry of the body – influencing physiological, emotional and cognitive

processes – it would appear that these physiological differences may have been brought about by attentional processes within the brains of the higher-skilled golfers. According to the theory, better players are more effective at encoding environmental information in order to execute the putt. Elite golfers have developed a higher level of automatic movement, and therefore are able to trust their swing and focus more attention on external goal-oriented factors, such as the target, ball or putting line, rather than on how their body feels. The physiological consequence is that the heart rate slows, and the lungs deflate, momentarily before the allimportant strike. However, when novices internalize their attentional focus, for example on the head or the grip, the heart rate accelerates and the lungs fill.1,2 With elite golfers externalizing thoughts more than beginners,3,4 we can begin to see how the integration of body and mind can improve the golfer’s focus and be a determining factor in putting success.

Heart rate during a putt 4 2

Mean heart rate change (bpm)

0 –2 –4 –6 –8 –10

g Mind over matter

–12 –14

Novice

–16

Experienced

–18

Elite

–20

–6 –5.5 –5 –4.5 –4 –3.5 –3 –2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time (s)

36

Mind and Body

Ensuring current thoughts are in the right place before making a putt can have dramatic effects on physiology. As shown in the graph, experienced golfers are able to lower heart rate response to a greater extent moments before making contact with the ball. This reflects an ability to construct a pre-shot ‘mind routine’ that focuses on environmental cues linked to the task and not internal cues from the body.

Control of heart rate Higher-order brain regions affect the control of heart rate by influencing the neural inputs to the heart, maintaining its muscle tone, and altering its pace.

During the putt, the prefrontal regions of the brain interpret task demands while the sensorimotor regions receive information about the body, creating a motor command to execute the stroke.

Heart rate is controlled by the competing sympathetic and parasympathetic nervous systems, which increase and decrease the rate, respectively. What happens in our brain can profoundly influence the heart rate response, reflected through the variability between beats.

Inhalation of air into the lungs leads to an increase in heart rate known as respiratory sinus arrhythmia, while breathing out increases parasympathetic nerve activity, lowering the heart rate.

g Brain and breath

The execution of a psychophysiologically complex movement like a golf putt requires a neural superhighway of connections sending and receiving signals to and from the brain. The neural pathways between the cardio-respiratory ‘machinery’ and the brain ‘mainframe’ are so interconnected that subtle changes in cognitive-attentional processes can have profound effects on heart rate and breathing response. Research has shown that training attentional focus and breathing should lead to more putts being holed.1–2

d Let it out The graph depicts the breathing patterns immediately prior to a 2.4 m (8 ft) putt in three different golfing abilities. Elite golfers are much more likely to exhale just before making contact with the ball, releasing muscle tension, removing unwanted thoughts and allowing focus on the external aspects of the putt. Inhale Hold Exhale

8%

19%

73%

21%

Elite

38% 60%

41% 24%

Experienced 16%

Novice

37

Of all the techniques used to play sport, the golf swing has perhaps been scrutinized more than any other. There are now literally hundreds of instructional books describing the golf swing, but many of these are based on anecdotal insights provided by elite players and their coaches. In this chapter, various aspects of the golf swing are considered from an evidence-based scientific perspective. Integrating theoretical and empirical research from the sub-disciplines of sports biomechanics and motor control, Paul Glazier and Peter Lamb tackle a series of important questions about the sequencing and timing of body segment rotations, the magnitude and variability of grip forces, and the transference of weight during the swing, among others.

chapter two

the swing Paul Glazier and Peter Lamb

What is the ‘summation of speed’ principle?

How can I co-ordinate my movements to maximize club head speed?

In recent years, the sequencing and timing of body segment motions in the golf swing have been popular topics for study by golf scientists, in part because of the more widespread use of automated 3D motion-capture technology. An important finding to emerge from this line of research is that the generation of club head speed in golf is governed by the ‘summation of speed’ principle.1 This principle states that to maximize velocity at the end of a series of linked body segments (known as a ‘kinematic chain’), the series should commence with the larger, heavier, inner (or proximal) body segments and proceed to the smaller, lighter, outer (or distal) body segments.2

Another study, by Cheetham and colleagues,4 has compared the kinematic chains of professional and amateur golfers. It was reported that the professional golfers exhibited significantly greater values than amateurs for the following variables: all average rotational accelerations and decelerations (except pelvis); all peak rotational speeds; all rotational speed gains (i.e. pelvis to thorax, thorax to arm, and arm to club); and peak linear club head speed.4 It was suggested that, in general, these results indicated that amateurs had poorer co-ordination, weaker power production and less efficient energy transfer between segments than professional golfers.

A number of biomechanical studies examining proximal-todistal sequencing in the golf swing have generally confirmed that, following the preparatory (backswing) phase, the action (downswing) phase starts with a rapid rotation of the pelvis (498 degree/s), followed by progressively faster rotations of the thorax (723 degree/s), lead arm (1165 degree/s) and club (2090 degree/s) as impact nears, before slowing during the recovery (follow-through) phase (representative data taken from Geisler3 for professional golfers).

Based on these findings, it would appear that analysing the motions of body segments in the kinematic chain could provide invaluable information for identifying faults and prescribing modifications to technique. With the increased availability and affordability of 3D motion-capture technology and its growing capacity to more accurately measure body segment motion in real time, this line of research could help professionals and amateurs alike to improve the efficiency of their swings and maximize club head speed.

Kinematic chains Professional

Pelvis

0

40

The Swing

2300

Time (s)

0

Amateur 2 Impact

2300

Top

Impact

Angular velocity (º/sec)

Thorax

Amateur 1 Top

Angular velocity (º/sec)

Arms

Impact

Angular velocity (º/sec)

Club

2300

Top

Time (s)

0

Time (s)

Accelerate to accumulate

Angular velocity (º/s)

Address 2300

Impact

Top

Finish

1688 1125 563 0 –563 –1.2

–0.9

g Smooth swing The kinematic chains for one professional and two amateur golfers during the downswing phase (adapted from Cheetham et al4). The professional exhibits smooth accelerations and decelerations, with each curve peaking higher and later than the previous one, and the club peaking at impact. Amateur 1 exhibits poorer accelerations and decelerations, lower angular velocities and the arm peaks before the thorax. Amateur 2 exhibits no overall decelerations of the pelvis and thorax before impact.

–0.6

–0.3 Time (s)

Club Arms Thorax Pelvis

0

0.3

0.6

o Phase change The graph shows changes in angular velocities of body segments in the kinematic chain during different phases of the golf swing. During the downswing phase (period between the top of the backswing and impact) there is a sequential increase in angular velocity from the most proximal segment (pelvis) to the most distal segment (arm) and golf club.

41

Does head movement hinder swing performance?

Should I keep my head still during my swing?

Head movement is a good marker for body movement in the golf swing, specifically the lateral thorax shift. Although thorax anterior–posterior (or forward–backward) tilt can be compensated for by knee and hip flexion–extension, lateral thorax shift typically coincides with lateral head movement. This may be the reason that coaches have long viewed head movement as having such importance. The ‘head still’ dogma was supported by the findings of Cochran and Stobbs,1 who proposed a ‘pendulum’ model with a fixed pivot point, or fulcrum, located midway between the shoulders of the golfer. The idea was that keeping the axis of rotation immobile should result in a repeatable swinging motion of the pendulum. However, recent research has shown that the axis does not remain still during the full swing.2 Simulations have also shown that immobilizing the fulcrum has a negative effect on club head speed.2 In fact, to keep the head perfectly still during the swing requires the golfer to dissociate their head movement from the rest of the body’s moving parts. It may be easier for the brain to couple head movement with other moving body parts than to try to operate each independently.3 Horan and Kavanagh4 have shown that head movement patterns for professional golfers are consistent but vary from individual to individual. A common assumption is that lessskilled golfers move their head too much compared with expert golfers, but Sanders and Owens5 have reported that, for a small sample of expert and novice golfers (six of each), novices actually displayed less total head movement throughout the swing compared with expert golfers. The experts, however, showed more consistent head movement during late downswing and through impact, keeping their head behind the ball through impact more than the novices. Coaches may use head movement as an indicator of body movement (particularly lateral shift), but for the full swing there is no reason to advocate a particular pattern of head movement – including the absence of head movement. 42

The Swing

a Head masters

It has been shown3 that – for putting and possibly also chipping – expert golfers move their head in an egocentric pattern (i.e. the club head moves away from the target, and the head moves towards the target) relative to the club as compared with beginners who move their head in an allocentric pattern (i.e. club head moves back, away from the target, and head also moves back). Expert golfers also felt that their head stayed still while performing the egocentric movement pattern, even though it didn’t, although the range of movement was minimal. It is recommended that golfers avoid the allocentric head movement pattern typically adopted by beginners.

Eye movement

Expert fixation Novice fixation

o Eye on the ball

Mann and colleagues6 showed that expert golfers fixate their focal gaze more consistently and for longer (red) on the ball, and on the target, compared with high-handicap golfers (blue). This phenomenon may give the feeling of a still head position during putting and may well be responsible for expert golfers reporting that their heads remained still during putting and in the full swing.

Head and putter movement

588 578

600 568

500 400

558

300

548

200 538

100 0

10

20

30

40

50

60

70

80

90

100

Putter Head

800

Putter displacement (mm)

700

700

588 578

600 568

500

558

400 300

548

200 538

100 0

10

Time (%)

20

30

40

50

60

70

80

90

Head displacement (mm)

Putter Head

800

Egocentric pattern (generally used by experts) Head displacement (mm)

Putter displacement (mm)

Allocentric pattern (generally used by novices)

100

Time (%)

Allocentric movement pattern Position of head at address

43

What is the ‘X-factor’ and what role does it play in hitting a golf ball far?

Does a greater body turn help me hit further?

The ‘X-factor’ is a buzzword often found in contemporary golf instruction manuals. It was first introduced by Jim McLean in a Golf Magazine article in 19921 and refers to the differential in degrees of rotation between the pelvis and thorax during the golf swing. Based on data subsequently published as part of a larger study by McTeigue and colleagues,2 McLean showed how five of the longest-hitting professionals of the PGA Tour had a larger X-factor at the top of the backswing than five of the shortest-hitting professionals. He proposed that a direct relationship exists between the pelvis–thorax separation angle at the top of the backswing and club head speed at impact – that is, a larger separation angle is generally associated with greater club head speed, and longer drives. Many coaches now advocate a restricted pelvis turn during backswing to maximize the relative angle between the pelvis and thorax. An increase in the X-factor during the early downswing has also been shown to be associated with higher club head speeds and longer distances. This move – called the ‘X-factor stretch’3 – involves the rotation of the pelvis back towards the target while the thorax is still either completing the backswing or is stationary at the top of the backswing. It has been hypothesized that, by increasing the separation angle between the pelvis and thorax during transition, the abdominal and oblique muscles are dynamically stretched, leading to a more forcible contraction and a greater transfer of energy to the thorax. Empirical support for the role of the X-factor stretch was initially provided by Cheetham and colleagues,3 who showed that a highly skilled group of golfers exhibited a significantly greater X-factor stretch than a lesser skilled group. Interestingly, they also found that no significant difference in the X-factor at the top of the backswing existed between groups. These findings led the researchers to suggest that the X-factor stretch is potentially more important than the X-factor when generating high club head speeds, although more recent research4, 5 has indicated that they are of equal importance. 44

The Swing

‘X’ marks the spot Pelvis axis alignment angle

Thorax axis alignment angle

–90°

–45°

–135°

0°

–180°

90°

Longest hitting Tom Purtzer (driving rank 4)

John Daly (driving rank 1)

48° 49°

39°

66° 114° 88°

Shortest hitting Lennie Clements (driving rank 141)

Lance Ten Broek (driving rank 148)

23°

24° 59°

63° 86°

83°

X-factor differences X-factor differential top of backswing

g Angle of separation

The ‘X-factor’ is defined as the separation angle between the pelvis and thorax during the golf swing, specifically at the top of the backswing. When viewed from above, the intersection of the pelvis axis (defined as an imaginary straight line running through the hip joints – red line) and the thorax axis (defined as an imaginary straight line running through the shoulder joints – blue line) in the horizontal plane forms an ‘X’, hence the term ‘X-factor’.

Higher-skilled players Lower-skilled players

Thorax rotation Pelvis rotation Differential

Mark Hayes (driving rank 37)

32°

41°

69°

37°

34°

71°

89°

Average (driving rank 161)

29°

100°

24°

26° 62°

71°

70°

88°

Mike Reid (driving rank 187)

19°

38°

50°

100°

Peter Persons (driving rank 175)

o Backswing and downswing Mean differences between highly skilled (scratch handicap or better) and low-skilled (15 handicap or higher) golfers in X-factor at the top of the backswing and maximum X-factor during the downswing, as reported by Cheetham and colleagues.3 On average, the highly skilled golfers stretched their X-factor by 19 per cent at the beginning of the downswing, which was significantly greater than the 13 per cent stretch exhibited by low-skilled golfers. However, there was no statistically significant difference between the two groups in the X-factor at the top of the backswing.

Average (driving rank 19)

59°

Tom Byrum (driving rank 158)

50°

44°

Jay Don Blake (driving rank 29)

39°

57°

48°

d ‘X’ statistics The longest- and the shortest-hitting golfers on the PGA Tour on average barely differed in the amount of thorax rotation (88° versus 89°) but they did differ in the amount of pelvis rotation (50° versus 65°).1 When expressed as a percentage of thorax rotation, the differential between the thorax and pelvis rotations, or the X-factor, accounted for 43 per cent and 27 per cent for the longest and shortest hitters, respectively. Interestingly, John Daly – the number one ranked driver in 1992 – had the third-largest pelvis rotation of all the tournament professionals analysed. He also had the largest X-factor. These findings indicate that, contrary to popular belief, a restricted pelvis rotation is not a prerequisite for a large X-factor. These findings also suggest that caution should be applied when attempting to extrapolate results from group-based analyses to specific individuals.

Tommy Armour III (driving rank 22)

X-factor differential during downswing

65° 88°

89°

45

What neuromuscular patterns characterize an effective golf swing?

What muscles do I use during my golf swing?

Knowledge of the muscles that are most active at various times during the golf swing is important, not only from a golf coaching standpoint, but also from a strength and conditioning perspective. Using a technique known as electromyography (or EMG), scientists have been able to shed some light on how the muscles work during the golf swing. By attaching electrodes to the surface of the skin adjacent to specific muscle groups or by inserting fine-wire indwelling electrodes directly into individual muscles, the magnitude and duration of electrical activity within the muscle(s) can be measured.

combined, these provide a reasonable picture of the sequencing and timing of muscle activity during the golf swing. Most studies have examined muscle activity during the following phases: backswing; forward swing; acceleration phase; early follow-through; and late follow-through.

Although it is impractical to analyse the action of all muscles simultaneously, a number of studies have considered the activation characteristics of key muscles of the trunk, shoulder, chest, forearm and lower limbs during the golf swing.1,2 When

The information presented here may help to identify where musculotendinous injuries may occur, and to direct muscle strengthening programmes that can increase the robustness of muscle and connective tissue to acute and chronic trauma. Further research is required on mid- to high-handicap golfers as most studies, to date, have focused almost exclusively on low-handicap or professional golfers. More studies investigating muscle activity in female golfers are necessary as much of the extant literature has considered only male golfers.

Muscle activity

46

The Swing

a Backswing

a Forward swing

The most active muscles during the backswing (the period between address and the top of the swing) are the right trapezius (upper, middle and lower portions), right rhomboid, right levator scapulae, left serratus anterior (upper and lower portions), and left subscapularis. (It is worth noting that the situation is mirrored for left-handed golfers.)

The most active muscles during the forward swing (between the top of the backswing and the horizontal position of the club during the downswing) are the right gluteus maximus (upper and lower portions), right gluteus medius, right biceps femoris, right semimembranosus, left adductor magnus, left biceps femoris and left vastus lateralis.

Muscle map

Trapezius

Levator scapulae Trapezius Subscapularis

Rhomboid

Serratus anterior Biceps brachii, long head Biceps brachii, short head External abdominal oblique Brachioradialis

Serratus anterior Triceps brachii Latissimus dorsi Extensor carpi ulnaris Gluteus medius Gluteus maximus

Sartorius

Adductor magnus Vastus lateralis Biceps femoris Semimembranosus

Vastus lateralis

a Mighty muscles

The main muscle groups recruited during the golf swing are listed here (right) and highlighted during the five phases of the swing (below). The more active groups in each phase are shown in progressively redder tints.

a Acceleration

a Early follow-

a Late follow-

The acceleration phase is the movement between the horizontal position of the club during the downswing and ball impact. The most active muscles during this phase are the serratus anterior, external abdominal obliques and left biceps femoris.

through The early follow-through is defined as the period between ball impact and horizontal position of the club during the follow-through. The most active muscles during this phase are the serratus anterior and left biceps femoris.

through The late follow-through is defined as the period between horizontal position of the club during the follow-through and the end of the swing. Here the active muscles are latissimus dorsi, external abdominal obliques, biceps femoris and gluteus maximus.

47

equipment: the glove

Golf is one of very few sports that see the performer wear only one glove, instead of a pair. Propelled by a better understanding and application of materials science and technology, the glove has come a very long way from its original concept in the late 1800s as a simple means of protection against unwanted calluses. Popular magazines of the time promoted a glove specifically targeted at golfers, with pleats offering more room for movement around the knuckles. These first gloves were generally either fingerless or backless and ensured that the hands remained blister-free.

It wasn’t until the 1930s, when professional golfers began to wear gloves, that their popularity grew. In addition to protecting the hand from wear and blistering from repeated swings, the glove also offered a layer between the backhand and club, thereby creating a firmer grip throughout the swing. Eager to try anything that might improve their game, touring professionals quickly adopted the glove as standard equipment. As new players appeared, they were more likely to have already begun playing golf with a glove, and so, by the 1950s and 1960s, it had become firmly embedded within the golfer’s bag. Modern breathable and waterproof materials, combined with new machining and sewing techniques, have led to today’s hightech piece of equipment.

Generating friction

g Get a grip The interaction between the glove, bare hand and club grip provides forces of friction that ensure, whether in dry or wet conditions, that the hands don’t slip relative to the club or to each other. At address, the outer surface of the glove and the grip remain in firm contact with each other, therefore locking together. This is known as static friction. As the club begins to move during the swing, the bare skin, inner glove surfaces, the glove’s outer surfaces and the grip can start to move if the club is moving relative to the hands. This gives rise to kinetic friction. 48

The Swing

Mathematically, the maximum friction available between the glove and grip (Ff) is a function of the materials comprising the two surfaces (reflected in the coefficient of friction, μ) and the grip force, which is the normal or perpendicular force pushing the two objects together (Fn).

F f = μF n If the glove (or grip) is worn or wet, the coefficient of friction will be reduced, making it more likely that the hands will slip.

Comfort and performance

Carefully placed mesh aids knuckle and finger flexion during the swing.

Advanced fabric technology ensures the material of the glove remains soft to the touch and keeps its shape.

Modern breathable materials and ventilation holes keep the hand cool and reduce unwanted moisture.

Ergonomic features provide support and eliminate discomfort, while ensuring even contact between glove and grip. Smooth bindings provide comfort when gripping the club with both hands, and elastic helps the fit of the glove.

Breathable Elasticated stitching is designed to mould to the grooves of the player’s hand.

o Gripping stuff The modern golf glove is the accumulation of years of research-driven development. Many features, such as strategically placed, ribbed contact points, meshed motion zones, and contoured stitching, create a glove that helps the golfer grip the club more comfortably.

Water repellent

a Material improvement

Fabric technologies have revolutionized the performance of sports clothing, and the humble golf glove has benefited from such advancement. Today, glove materials are combined to provide a breathable, lightweight and comfortable membrane that also repels external moisture.

version A

Breathable material

version B

49

What are the core movements that set Tour pros apart?

What movements help Tour pros to hit the ball better?

From watching the Tour pro on television, most people can easily recognize their swings as powerful and efficient. Not surprisingly, the bulk of biomechanical studies1 have confirmed that professional golfers achieve faster body rotation and a better-timed sequence of the rotating segments – both of which lead to faster club head speed compared with highhandicappers. These differences between professionals and less-skilled golfers seem fairly obvious, but what exactly are the characteristics of the swing which lead to faster body rotation and, ultimately, faster club head speeds?

d Tilt-shift The image of the professional golfer (right) demonstrates two key characteristic core movement patterns at the top of the backswing. First, the thorax is tilted away slightly from the target (white line), keeping close to the address position, and second, the pelvis has maintained its lateral position during the backswing (blue line). These core movements are possible because of a balanced interaction with the ground. The professional golfer also shows reduced lateral shear forces and a constant pressure on the medial aspect of each foot (red lines). In contrast, the high-handicap golfer (left) has shifted the pelvis laterally (blue line), tilted the thorax towards the target (white line) and allowed foot pressure to move to the lateral aspect of the rear foot (red lines).

Top of backswing High-handicap golfer

Professional golfer

Minimal change in thorax tilt from address position

Thorax tilt towards target

Lateral pelvis shift away from target

Foot pressure near outside of foot

50

The Swing

Minimal change in lateral pelvis position from address position

Constant pressure on inside of each foot

There are many finely tuned and highly co-ordinated movements of the arms, hands and club that contribute to faster club head speed, but limb movements represent the end of the kinematic chain and these must be preceded by proper movements in the core – the pelvis and thorax. In terms of core movement, there are several key moves the professional golfers make that distinguish them from the average golfer. In particular, professional golfers maintain lateral stability and posture during the backswing to a greater extent. Core stability can be seen by looking for lateral tilting of the thorax and lateral shifting of the pelvis – professionals show minimal change in both of these key indicators during the backswing.2,3 In the downswing, the professionals rotate their pelvis towards the

d Read the hips A side-on view at impact: the professional golfer (right) has rotated the pelvis towards the target. The high-handicap golfer on the left has kept the pelvis square to the target at impact, limiting club head speed. In addition to rotating the pelvis towards the target, the professional has also shifted the pelvis towards the target during the downswing, evidenced by the right heel being slightly raised off the ground at impact.

target earlier than the average golfer – this is commonly referred to as ‘clearing the hips’. In fact, professional golfers begin the downswing with pelvis rotation, whereas the average golfer tends to begin the downswing with thorax and shoulder rotation. Finally, at impact, the professional’s pelvis and thorax are both opened towards the target.3 These core movements are achieved as a consequence of the golfer’s interaction with the ground. Professional golfers impart greater anterior–posterior shear forces and reduced lateral shear forces on the ground compared with less-skilled golfers. The skilled golfer’s foot pressure is to the inside (medial) and towards the heel (posterior) of each foot.4 This interaction with the ground promotes stability at the transition of the backswing. This then sets up a quick, powerful rotation during the downswing, which is initiated by the anterior–posterior shear forces. The average golfer struggling with low club head speed could learn a great deal from studying the core movements of professional golfers.

Impact Professional golfer

High-handicap golfer

Pelvis has not rotated towards the target

Pelvis has rotated towards the target

Weight has not shifted to left side

Weight has shifted to left side

51

Is weight transference significant?

How much should I shift my weight during the swing? Weight transfer styles

Weight transference is a coaching term used to convey the proportion of the golfer’s total weight that should be distributed over each foot during the swing. More accurately, biomechanists have defined weight shift as the change in the proportion of total downward force under the front foot throughout the movement.1 According to popular coaching manuals, for full swings the weight should begin balanced evenly between both feet (about 50 per cent each) at address.1,2 Conventional coaching advocates that the weight should then shift towards the rear foot during the backswing and then rapidly towards the front foot in the downswing, and research seems to support this. However, other patterns of weight transfer have been identified which are associated with expert performance. Two distinct weight-transfer techniques – the so-called ‘frontfoot’ and ‘reverse’ styles – have been identified,1 while a swing technique called ‘stack and tilt’ is anecdotally popular among some players and coaches.3 The front-foot style matches the conventional idea of weight transfer. The reverse style is distinguished by the weight shifting back towards the rear foot during mid-downswing. The stack-and-tilt swing, in terms of weight transfer, can be generalized as ‘staying centred over the ball’ rather than shifting weight towards the rear foot during the backswing. Axial rotation and lateral tilt of the thorax achieve comparable angular speed profiles throughout the downswing.4 Given that there is room for the thorax to tilt and the pelvis to shift laterally, this action would explain the weight shift towards the front foot in the swing. Furthermore, the peak in downward force occurring before impact (event ED) represents the force required for decelerating pelvis rotation and lateral movement, which is the beginning of the kinematic chain.5 In light of these scientific findings, the reverse-style weight transfer appears to be associated with exceptional performance. An awareness of the two patterns presented here, and experimentation with pressure mats, will enable the player to explore which swing technique fits best. 52

The Swing

TA

MB

19 54

LB

17

22

24

50

Front-foot style % weight under front foot Reverse style % weight under front foot

d Feel the force Here the total force is visualized as a vector, with its length representing the magnitude of the force, and its direction showing the direction of the ground’s reaction force to each foot. At TB, vertical force (weight) is greater under the rear foot (foot furthest away from target), shown by the longer rear foot vector. At ED, the rear foot vector points posteriorly, which means the rear foot is pushing anteriorly into the ground. The front foot (foot closest to the target) is pushing in the opposite direction (posteriorly). The opposing directions of the ground reaction forces by each foot cause rotation. At BC, the directions of both force vectors have reversed. Total force vectors TA

TB

Ground reactive force

ED

BC

d Weight-watching The nine events for a lowhandicap golfer: take-away (TA), mid-backswing (MB), late backswing (LB), top of backswing (TB), early downswing (ED), mid-downswing (MD), ball contact (BC), followthrough (MF), finish position (FP).1 The percentage bars

TB

represent average values for the proportion of total vertical force under the front foot (e.g. 0 per cent = no weight under front foot, 100 per cent = all weight under front foot). Red values correspond with the front-foot group and blue values with the reverse-style group.

ED

MD

BC

MF

FP

20 42

40

42 56

59

67

80

82

80

59 78

Front-foot style 1400

TA

MB

LB

BC ED MD MF

TB

FP

1200 1000

Average downward force (N)

800 600 400 200 0

Backswing

Downswing

Follow through

Reverse style 1400

TA

MB

LB

TB

BC ED MD MF

FP

1200 1000 800 600

g Fancy footwork

The downward force for each of the golfer’s feet is shown: red for the front foot, black for the rear foot. The top graph is an example of the downward forces involved with a swing consistent with the front-foot style, and the bottom one of a swing consistent with the reverse style.1 In the reverse group the weight starts to shift back towards the rear foot at ED. The peak in front-foot downward force (at ED) is linked to the start of the kinematic chain. Notice that the sum of vertical forces for both feet does not necessarily equal the golfer’s weight (weight in N = mass in kg x acceleration due to gravity at 9.8 m/s2). Because of angular momentum, the rotation can drive the golfer into the ground or lift the golfer off the ground. For this reason some players’ heels leave the ground during ball contact.

400 200 0

Backswing

Downswing

Follow-through

Front foot downward force Rear foot downward force

53

SCIENCE

IN ACTION

assessing the risk

Being a good golfer is not just about being able to hit the ball well and consistently, but also about knowing which shots to make in which circumstances – making the right decision at the right time in the right place. This mostly means setting up each shot to give you the best chance of making par or better. How a player decides on the most appropriate shot at any one time is governed by many factors. Is it best to play it safe, or take a risk? Do you ‘take on’ the hazard – water or sand – or avoid it? How a player is performing against their handicap or an opponent, their position on the leader board, or their current mental state following a run of good or bad luck can all dictate whether a conservative or risk strategy is selected. Although it seems obvious that a more able golfer would take fewer risks throughout their round, given their aptitude and the potential cost of the risks, and that a novice would have more to gain from a riskier strategy, this may only be partly true1: research does also reveal that our general risk-taking behaviour throughout the 18 holes may say more about our character than our score.2 Top golfers instinctively select a strategy for each shot based on the environmental cues they observe and their past experiences. Firstly, by scanning the hole they are consistently assessing the risks. They evaluate the probability of a particular shot type being successful, and assess the penalty if it goes wrong and the reward if they pull it off. How we assess risk is very much dependent on what we have to lose if it all goes wrong. Even for players of a high standard, playing it safe does not mean avoiding the rough – or even hazards – as much as ensuring that the next shot will enable them to use a predictable swing, resulting in accurate length and line.

54

The Swing

a Risk assessment Assessing the risk of any shot comes down to two important factors: the likelihood of success and the severity of the penalty if it all goes wrong. Having assessed the risk, here Martin Kaymer of Germany plays a tee shot across a wide expanse of water during his first round of the French Open at Le Golf National.

55

What is the optimal pattern of wrist torque for maximizing club head speed?

Can the ‘late hit’ help my driving distance?

There is a lot of discussion about the release of the wrists during a swing as impact approaches. The so-called ‘late hit’, popular in many coaching manuals, is characterized by keeping an acute angle between the lead forearm and the club shaft for as long as possible during the downswing. Cochran and Stobbs proposed that although the ‘natural wrist release’ – caused by centrifugal force of the swinging club – provides plenty of club head speed, slightly more could be squeezed out of the swing if the wrists actively applied torque late in the downswing.1 They also noted that in order for this strategy to work the wrist angle would have to be released later than in the natural release.

wrist action’, similar to the delayed wrist action but followed by an active wrist torque to accelerate the club into the ball. Simulation studies have agreed that the delayed-active torque technique offers potential for maximizing club head speed.2,3,4 Sprigings and Mackenzie showed that if wrist torque is applied to maintain the wrist–shaft angle until the lead arm reaches ‘eight o’clock’ when viewed from the front (the ‘delayed wrist action’), at which point the torque is applied in the opposite direction to actively release the wrists, club head speed could be maximized (by about 1.6 per cent faster than natural release). However, the timing window in which these torques need to be applied is extremely sensitive, which suggests that the benefits associated with delayed-active wrist torque are difficult to achieve. If the More recently, many studies have looked into optimizing the active torque is mistimed by just 50 ms (half the time it takes to release behaviour of the wrists before impact. In general, three blink), club head speed would be slower than the natural release. main wrist release strategies have been investigated: the This sensitivity to timing suggests optimizing wrist action is highly ‘natural release’, which requires no muscular torque; a ‘delayed dependent on the player’s proprioception, or feel. All of which suggests that, for the average golfer, it is probably more wrist action’, in which wrist torque is applied to maintain the worthwhile keeping a relaxed grip and trying to release naturally. wrist angle and promote the late hit; and the ‘delayed-active Delayed-active release

A

A

56

The Swing

Delayed-active release D

B

F

C

G

D

Delayed wrist action

The sequence on the left represents a swing with o Optimized release The swing sequence shows the optimal wrist release in the 4 drive. When the left arm is at ‘nine o’clock’ muscular force is applied to maintain the wrist the delayed-active (optimal) wrist torque from Sprigings and Neal. The wrists release angle. Once the left arm reaches about ‘eight o’clock’ the wrists should forcefully release because of the centrifugal force acting on the club, and at ‘B’ muscular torque is applied the club through ball contact. Both wrist torques must work in concert with each other – if to further release the wrists and accelerate the club. On the right, no muscular torque is the wrist angle is actively released too early the advantage of applying wrist torque is lost. applied to release the wrists, only the centrifugal force acting on the club. In simulation the delayed-active release reached a club head speed of 158.4 km/h (98.4 mph) and the Natural release natural release 145.5 km/h (90.4 mph).

d Delayed and natural releases

Natural release A

A

D B

F C

GD

57

How do grip forces change during the golf swing?

How firm should my grip be?

The grip is one of the most important facets of the golf swing because it represents the only interface between the golfer and the club through which all force and energy must be transmitted. Many golf instruction manuals recommend that the grip should be kept as loose as possible to allow a full and unrestricted release of the golf club, but also firm enough to prevent the club from slipping, particularly during the impact phase. A loose grip can also help to maximize the ‘feel’ of a golf shot and reduce the likelihood of overuse and repetitive strain injuries occurring in the hands, wrists and forearms. Another recommendation that appears to be prevalent in the golf coaching literature is that grip firmness should remain fairly constant throughout the golf swing.1 However, a basic mechanical analysis indicates that this supposition cannot be correct. When a golf club is swung, centrifugal forces are generated, which are proportional to the amount of acceleration and deceleration of the golf club. These load forces have been estimated to be up to 450 N for very fast swings.2 Additional load forces are also generated during the impact phase through collision between the club head and the golf ball and turf, the magnitudes of which depend on their respective physical characteristics and relative momentum at impact. Grip forces, therefore, need to be adjusted simultaneously or slightly ahead

of fluctuations in load forces to avoid an inefficient transfer of force and energy as a result of the golf club slipping. Owing to difficulties with measuring grip forces, only a few biomechanical investigations have focused on this aspect of the golf swing. Budney3 measured grip forces under the last three fingers of the left hand, on the base of the first three fingers of the right hand, and under the left thumb, using an instrumented driver fitted with strain gauges. Although individual differences were reported, the three golf professionals analysed exhibited grip forces which were closer to those recommended in the coaching literature than did the three amateur golfers. However, owing to the small number of golfers analysed in this study, the generality of these findings is limited. In a more extensive recent study, Komi and colleagues4 showed that 20 golfers (male and female), regardless of playing ability, had their own unique grip force ‘signature’ – that is, grip forces were highly consistent for each golfer over repeated shots but varied considerably between golfers. Certain trends were evident across golfers, however, such as local peaks in grip force just before and after impact, and an overall higher force on the left hand than on the right hand for nearly all golfers tested. The data here are for right-handed golfers but it is worth noting that the situation is mirrored for left-handed golfers.

Measuring grip forces

g Handy hints

Force sensors use a semi-conductive ink that is applied between electrical contacts and thin polyester sheets, giving the sensors a resultant thickness of just 0.1 mm. These extremely thin and lightweight sensors can be fitted around the circumference of the golf grip, or attached to the gloves themselves, to allow the changing forces at numerous locations to be measured simultaneously.

58

The Swing

Grip forces

Professional 30 20

Right hand

10 0 30 20

Left thumb

g Getting a grip

Even as far back as the late 1970s, scientists were able to measure grip forces throughout the swing by using a modified grip equipped with a series of strain gauges. Results collected from professional and amateur players began to reveal demonstrable differences in force patterns between skill levels.3

10 0 30 20

Left hand

10 1.0 0.8 0.6 0.4 0.2 0

Start of backswing

Top of Impact backswing

Professional 1 Professional 2 Professional 3

0 Force (N)

400 Force (N)

Time before impact (s)

Amateur

200

30 20

Right hand

10 0 30 20

Left thumb

10

0

-0.5 0 0.5 1

Time (s) Left hand Right hand Mean total

0 30

o In the swing Analyses of grip forces using grip and glove sensors in conjunction with high-speed video have 10 revealed highly individualized grip force patterns across 0 golfers regardless of playing standard.4 An example of Force force–time profile for the left and right hand, and both (N) hands combined, is shown here, along with six key points and corresponding swing position images. 20

Left hand Time before impact (s)

1.0 0.8 0.6 0.4 0.2 0

Start of backswing

Top of Impact backswing

Amateur 1 Amateur 2 Amateur 3

59

Can biomechanical analyses help to increase consistency?

Can the ‘swing plane’ improve how I hit the ball?

The ‘swing plane’ concept was originally introduced by Seymour Dunn in the 1920s but was popularized by Ben Hogan during the 1950s in his classic instructional text, Five Lessons: The Modern Fundamentals of Golf.1 The swing plane is now generally considered to be an imaginary two-dimensional surface, extending from the centre of the golf ball through the top of the golfer's sternum, along which the club head should travel during the swing. It is thought to be an important aid to improving the swing because it supposedly enables the golfer to deliver the club more consistently at impact, leading to less dispersion of shot outcomes. There have been several biomechanical investigations into the swing plane concept but these have typically been equivocal and contradictory. For example, in three-dimensional kinematic studies by Vaughan2 and Neal and Wilson3, it was found that the plane of the shaft of the golf club was not constant for any substantial period of time during the golf swing. In contrast, Lowe and Fairweather4 reported that the downswing and follow-through phases of the swings of expert golfers were approximately planar. More recently, Coleman and Anderson5 showed that it was possible to fit a single plane to the motion of the golf club during the downswing for a group of experienced golfers, but the fit varied between golfers and also between clubs (that is, a pitching wedge, a 5-iron and a driver). Despite being the focus of a number of scientific investigations, the swing plane still remains a contentious concept and further empirical research is warranted. However, Jenkins1 has suggested that the concept might be used as an ‘idealized replica’ to help golfers develop a mental image of what their golf swing should look like in their quest to improve. Indeed, in his original writings, Hogan noted great improvements in the techniques and performances of golfers that he had personally taught after encouraging them to visualize the backswing and downswing movements along the swing plane. 60

The Swing

g Plane simple

Ben Hogan famously visualized the swing plane as a large pane of glass running from the ball parallel to the target line and placed over the golfer’s head so that it rests on their shoulders, the theory being that the shoulders, arms and hands should all move along this plane throughout much of the golf swing. The angle of inclination of the swing plane is determined by the golfer’s stature and the distance they stand from the ball at address, which is dictated by the club used (for instance, a pitching wedge, 5-iron, or a driver; see above).

o Got that swing No two golfers swing the golf club along identical swing planes. Tiger Woods (above) approximates to the swing plane during both the backswing and downswing, whereas Jim Furyk (above right) moves above and below the swing plane during different portions of the backswing and downswing. Both are Major champions.

a Computer aid

Recent research has contradicted Hogan’s original ideas by showing that the trajectories of the shoulder, elbow and wrist joints during the swing do not move along a single plane whereas the club head does, at least for a portion of the swing. This computer-generated stickfigure shows a real golfer nearing impact.

61

Is there evidence for an optimum movement model?

Can a perfect swing be achieved?

It is tempting to treat the golf swing technique as an optimization problem, in that every position the golfer moves through has an ideal. This is the approach Mann and Griffin1 attempted to support by combining the swings of over 100 professional golfers. However, while it might be theoretically possible to create a simulation or robot capable of such a perfect, repeatable sequence, the human player has many more variables to contend with, both internal and external, so that a single, fixed swing pattern is not what’s required. In other words, each player must consider their own strengths and weaknesses, which have arisen from their past experience and can be psychological as well as physiological. The player must then use that knowledge to simplify the task of co-ordinating nearly 800 separate muscles, which must be precisely controlled to create a functional swing.2 Storing the vast number of configurations into which our body segments could be arranged theoretically requires computational power beyond the brain’s neurophysiological limits – and yet, of course, humans are able to co-ordinate highly complex patterns of movement, including the golf swing, with apparent ease and fluidity. A leading explanation for our ability to overcome the seemingly infinite number of possible swings to produce a functional swing comes by way of synergies.3

A synergy is a conceptual linkage of parts (such as muscles) that reduces the information the brain needs to supply to operate the movement. When coaches refer to ‘moves’ in the golf swing (for example, lead the downswing with the hips) they are supplying a small amount of information that collectively represents a great deal of information. Synergies operate in a similar way. What makes a golf swing good is not just the positions it moves through but, probably more importantly, the stability of these temporary synergies which are very individualspecific and, if stable, will lead to predictable golf shots. Biomechanical studies confirm that individual variation is the rule rather than the exception and, although swings of good golfers may have certain commonalities, each golfer still has their own signature.4,5 It may be reasonable to imagine a perfect swing for an individual playing a specific shot, but throughout a round of golf, a tournament or a career, to perform well the individual must be able to adapt the swing to suit the specific situation and the shot being played. Instead of a perfect swing, it is probably better to talk about an adaptable swing that adheres to general biomechanical principles and can accommodate many different situations. Practice drills which improve kinaesthetic awareness are probably very influential in improving golf-specific synergies.6

Creating a functional swing A

B

C

g How a golf swing works

One approach to explaining a functional swing is shown here:7 the golfer uses a previous state (A) to predict a future state in the swing (B); when the golfer arrives at the predicted state (B), sensory information is compared with the expected information and used to make the necessary adjustments for future states (i.e. body position and velocity at impact – C). This model allows for uncertainty at the intermediate stage in the movement (B), after which error is reduced at the critical instant (time of impact) given a known target (ball location).

62

The Swing

Model movement

o Concepts of swing control The left-hand image illustrates the concept consistent with the ‘perfect swing’ school of thought: the individual body parts must be controlled independently by the brain. The right-hand image shows the alternative concept: synergies are created and controlled by the brain as a unit rather than individual parts. If one part is ‘out of position’ its linkage to other parts makes compensatory movements possible. Notice also how the interactions in the second image reduce the amount of information needed by the brain to control the golf swing. These images are adapted from the original conception by Michael Turvey.2

d Measuring synergies

Two variables recorded at impact in the golf swing can be plotted against each other to show whether they represent a synergy. Elongated clusters of data points along the diagonal line indicate a compensatory movement – a synergy: if one component of the swing is out of position (if its value is too high or too low) the other variable will compensate to achieve roughly the same outcome. In some cases, a certain amount of variability in the golf swing is a good thing because it affords the golfer flexibility and adaptability for new and unexpected situations.

Compensatory movements NOT a synergy

A synergy

Stronger synergy

Variable 1

Variable 1

Variable 2

Variable 1

Variable 1

Variable 2

Weaker synergy

Variable 2

Variable 2

63

While a golf club is built from only three components, the technical elements of its design and performance are as varied as the golfers who play the game. Golfers vary tremendously in their size, strength, athletic ability and swing characteristics. A golf club with particular technical specifications will perform completely differently in the hands of different golfers. Matching each golfer with the right golf equipment that will enable them to play to the best of their ability is a specialized field within the game, called clubfitting. Accurate clubfitting requires a scientific understanding of how the different swing characteristics of golfers interact with the technical differences in golf equipment to result in differences in shot performance. In this chapter, Richard Kempton reveals why technical performance differences occur in golf equipment and how they are selected for each golfer, bringing the science of equipment right into the 21st century.

chapter three

the equipment Richard Kempton

Is there an optimum driver length?

Will I hit the ball further with a longer driver?

Probably one of the biggest myths in the game is that a longer driver will automatically produce more distance than a shorter one for all golfers. A longer driver certainly can result in longer drives, but it’s definitely not a universal truism. Ultimately the distance any golfer is theoretically capable of driving a golf ball will depend on how hard they hit it (i.e. club head speed at impact). Whether or not that will actually result in maximum distance depends on whether the impact results in the golf ball leaving the club face at the highest possible velocity, combined with the optimum launch angle, and with the optimum amount of spin to produce the optimum trajectory and landing angle for the ground conditions. There is no single optimum combination of launch angle and spin that will produce maximum distance for all golfers, because that will vary with initial ball speed and angle of attack (the upward or downward path of the club head at impact). A longer shaft should produce more club head speed by virtue of the increased radius of the arc described by the club head. It’s even possible to calculate how much extra club head speed an extra 2.5–5.0 cm (1–2 in) of shaft length will theoretically produce. However, golfers react to the weight and balance (assembled moment of inertia or swingweight) of a club, the way it feels, and even the way it looks, so – in practice – a longer shaft may not result in more club head speed. A longer shaft can even reduce club head speed rather than increasing it, if its swingweight (or more correctly the moment of inertia of the assembled club about the end of the shaft, which coincides roughly with the wrist joint of the upper hand) is greater than the golfer can swing and release efficiently. As a result, when driver lengths are increased, it is normally necessary to reduce the clubweight – usually most easily achieved by installing a lighter shaft. Assuming that the driver head is of the correct loft and configuration to provide the optimum launch angle, spin rate and trajectory, increasing driver distance is actually about producing more ball speed, and that doesn’t necessarily correlate with club head speed. 66

The Equipment

Factors affecting drive distance

Spine angle Golfer’s athletic ability

Club head feel Grip weight Club weight (head weight + shaft weight + grip weight) Club balance point Shaft length Club head COG location

Shaft bend profile Driver face loft Impact point

Club head weight

o Finding balance There’s more to driving distance than driver length. A driver’s ‘balance’ (swingweight or moment of inertia) is affected by a number of other factors: club head weight, the club head centre of gravity relative to the end of the grip, the weights and balance points of the shaft and grip and even the ratio of the club head weight to the shaft weight.

Smash factor and distance CLUB SPEED (km/h)

SMASH FACTOR (initial ball speed divided by club head speed) 1.50 1.49 1.48 1.47 1.46 1.45 1.44 1.43 1.42 1.41 1.40 1.39 1.38 1.37 1.36 1.35 INITIAL BALL SPEED (km/h)

144.8 217.3 215.8 214.4 212.9 211.5 210.0 208.6 207.1 205.7 204.2 202.8 201.3 199.9 198.4 197.0 195.5 146.5 219.7 218.2 216.8 215.3 213.9 212.4 210.8 211.0 207.9 206.5 205.0 203.6 202.1 200.7 199.2 197.8 148.1 222.1 220.6 219.2 217.6 216.1 214.7 213.2 211.8 210.2 208.7 207.3 205.8 204.4 202.8 201.3 199.9 149.7 224.5 223.1 221.4 220.0 218.5 217.1 215.5 214.0 212.6 211.0 209.5 208.1 206.5 205.0 203.6 202.1 151.3 226.9 225.5. 223.9 222.4 220.8 219.4 217.9 216.3 214.8 213.2 211.8 210.3 208.7 207.3 205.7 204.2 152.9 229.3 227.9 226.3 224.8 223.2 221.8 220.2 223.5 217.1 215.7 214.0 212.6 211.0 209.5 207.9 206.5 154.5 231.7 230.1 228.7 227.1 225.6 224.0 222.4 221.0 219.4 217.9 216.3 214.7 213.2 211.6 210.2 208.6 156.1 234.2 232.6 231.1 229.5 227.9 226.4 224.8 223.3 221.6 220.2 218.5 216.9 215.5 213.9 212.3 210.8 157.7 236.6 235.0 233.4 231.9 230.3 228.7 227.1 225.5 224.0 222.4 220.8 219.2 217.6 216.1 214.5 212.9 159.3 239.0 237.4 235.8 234.2 232.6 231.1 229.5 227.9 226.3 224.7 223.1 221.4 219.8 218.2 216.6 215.2 160.9 241.4 239.8 238.2 236.6 235.0 233.4 231.7 230.1 228.5 226.9 225.3 223.7 222.1 220.5 218.9 217.3

o Effect on distance A longer driver can increase distance, but only if it enables you to increase your club head speed and your ball speed. That will depend on what happens to your smash factor Ball speed = (club head speed) x (smash factor) when you swing a longer driver. If your smash factor improves – or the fall in smash factor is minimal – and you are able to generate more club head speed (and you can maintain or improve your angle of In the club attack, launch angle and spin rate), you will see a distance increase (but possibly not as much as you Driver fitting is a complex balancing act between club think). However, if your smash factor drops too much (or your angle of attack, launch angle and spin rate change for the worse), you could actually lose distance. This table helps to show why: to convert an length, shaft and club weight, club balance, club head increase or decrease in ball speed to an approximate yardage change, multiply by a factor of 1.7–1.8. loft and club head face angle and feel. All these elements (Note that for many golfers, a 2.5 cm (1 in) longer driver will not increase their club head speed by more affect club head speed and the ability to hit the ball than 3–5 km/h/ 2–3 mph, unless the total club weight is also significantly reduced.) NEW 068-069 g3 consistently on face centre, as well as the launch angle, grouped object

A longer driver, even one fitted with a lighter shaft, may – and usually will – result in the ball being struck less consistently on face centre and less squarely, which will affect the ball speed to club head speed ratio (the ‘smash factor’). For every golfer there will come a point at which the law of diminishing returns starts to operate, where (a) a longer driver gives more club head speed, but the smash factor drops to a level which results in no increase in ball speed and distance, or even a reduction in ball speed and distance; or (b) a longer driver results in less club head speed and less ball speed and distance. That compromise is ultimately a matter of golfer choice, but remember that it is easier to score from the fairway than from the rough.

no line weights..

spin rate, trajectory and spin axis tilt.

o Impact zone As the ball impact shifts away from the centre of the club face, both the coefficient of restitution and the smash factor will decrease, resulting in reduced distance and accuracy. 67

How far can a golfer drive the ball (step 1)?

How can I maximize my drive distance?

For any combination of altitude, ground and weather conditions, the maximum distance any golfer should theoretically be able to hit a driver can be estimated reasonably accurately from their club head speed and a knowledge of ballistics. On normal, level fairways in completely still conditions, at sea level, there is no technology permissible under the Rules of Golf that will enable a golfer with a sub-145 km/h (90 mph) club head speed to drive the ball 275 m (300 yd). However, in order for a golfer to achieve maximum distance, all three of the following conditions will need to be met: maximum club head speed is attained; the ball is struck on the area of the face where the coefficient of restitution is highest to maximize the smash factor and thus the initial ball speed; the combination of the launch angle (the angle at which the ball leaves the club face relative to the horizontal) and its initial spin rate provides the best possible trajectory and landing angle for that initial ball speed. As a result, maximizing driver distance requires a two-pronged approach. Step 1: optimizing for club head speed and impact consistency The length, total weight and ‘club balance’ of a driver (its swingweight or moment of inertia) all potentially affect club head speed, but in different ways – and, as stated above, simply maximizing club head speed will not automatically produce maximum distance unless both the initial ball speed and the trajectory are also optimal. The same three things also affect a golfer’s ability to impact the ball squarely and on face centre and the degree of accuracy and consistency they will achieve with it, so there is almost always a need to strike a compromise between maximum ball speed and acceptable accuracy. That compromise is ultimately a matter of golfer choice, but remember that it is easier to score from the fairway than from the rough.

68

The Equipment

A lighter driver can allow a golfer to increase their club head speed and thus potentially hit the ball further but, for many golfers, the distance increase will not be significant unless the club total weight is reduced by 20 g or more compared with their current driver – but accuracy/consistency may suffer, unless the assembled swingweight or moment of inertia is maintained at the level that the player needs. In very general terms, increasing the length of a driver by a couple of centimetres could potentially add 6.4–7.3 m (7–8 yd) to a golfer’s driving distance – provided that they can still maintain their smash factor at the same level as with a shorter club, that its total weight, swingweight or assembled moment of inertia do not increase above the thresholds that the golfer can consistently handle, and that accuracy and consistency are still acceptable. How do you know which combination of club length, total weight and swingweight/moment of inertia will do all these things? Your best option is to find a competent clubfitter who can not only work all that out for you, but also take care of the second aspect of maximizing your driving distance: determining the optimum combination of driver head and loft, shaft flex, and shaft bend profile for the way you swing the club (i.e. your club head speed and angle of attack) and the conditions on the courses you generally play. The two tables opposite show clearly that, for a given club head speed (assuming that the club is set up to allow the golfer to achieve the highest smash factor possible with a conforming driver), the combination of launch angle and spin rate needed for maximum distance depends not only on angle of attack (AOA), but also on whether the driver is to be optimized for maximum carry distance or maximum total distance.

Optimization for maximum total distance

Optimization for maximum carry distance1

a Maximizing distance The tables (right) show the distances that should be achievable for range of club head speeds (column 1) and angles of attack (column 2), depending on whether the driver is fully optimized for maximum carry (top table) or maximum total distance (bottom table). With a ‘Tour’ type ball, in still conditions at sea level and on normal fairways, the launch angles (column 3) and spin rates (column 4) will produce the distances given in columns 5 and 6 when the dynamic loft at impact is as shown in column 7. Column 7 ‘translates’ the dynamic lofts into actual driver lofts (to the nearest 0.5 degrees), provided that all three of the following assumptions are true: 1) on-centre impact, (2) shaft bending adds 1.5 degrees of loft dynamically at impact and (3) the golfer’s swing mechanics add NO loft dynamically. (Do not assume that the actual loft of any driver will be as marked unless it has been checked in a gauge.) If a golfer with a 145 km/h (90 mph) club head speed opts to have a driver optimized for maximum total distance (bottom table), the data shows that he will need about 5.5 degrees more driver loft with a –5 degree (negative or downward) angle of attack than if his attack angle were +5 degrees (positive or upward). The combination of a more upward attack angle and a lower driver loft will produce just over 22.9 m (25 yd) more carry and almost 27 m (30 yd) more total distance than the higher loft/ negative AOA combination. Both tables are adapted from data collected and analysed by the makers of the TrackMan™ launch monitor, Trackman a/s, Denmark (www.trackman.dk).

Club head speed (km/h)

Attack Launch angle angle (degree) (degree)

Spin Carry rate distance (rpm) (m)

Total distance (m)

Dynamic Approx loft driver loft (degree) (degree)

120.7 128.7 136.8 144.8 152.9 160.9 169.0

–5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5

3722 130.8 3121 140.8 2720 150.0 3652 146.3 3179 156.4 2648 165.5 3669 160.0 3164 171.0 2596 180.1 3689 174.7 3093 185.6 2633 195.7 3626 198.3 3114 200.3 2595 211.2 3722 203.0 3118 211.2 2538 225.9 3645 216.7 3038 229.5 2563 240.5

151.8 162.8 171.0 160.9 171.0 180.1 182.0 192.9 203.9 196.6 208.5 218.5 213.0 223.1 234.1 223.1 235.8 248.7 237.7 251.5 263.3

18.2 19.2 21.8 16.2 18.3 20.3 15.0 17.1 19.1 14.0 15.8 18.5 12.6 15.0 17.6 12.2 14.3 16.7 11.1 13.2 16.2

14.6 16.3 19.2 12.9 15.5 18.0 11.9 14.5 17.0 11.1 13.4 16.4 9.9 12.7 15.7 9.6 12.1 14.9 8.7 11.2 14.5

21.5 17.5 15.5 19.5 17.0 14.0 18.5 15.5 12.5 17.5 14.5 12.0 16.0 13.5 11.1 15.5 13.0 10.0 14.5 11.5 9.5

Optimization for maximum carry distance

Optimization for maximum total distance1 Club head speed (km/h)

Attack Launch Spin Carry angle angle rate distance (degree) (degree) (rpm) (m)

Total distance (m)

120.7 128.7 136.8 144.8 152.9 160.9 169.0

–5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5 –5 Level +5

166.4 14.9 178.3 15.3 188.4 17.1 171.9 12.8 182.0 14.3 191.1 16.5 196.6 11.9 208.5 13.8 220.4 15.6 211.4 11.0 224.0 12.8 236.8 15.3 225.9 10.2 239.6 12.3 252.4 14.4 239.6 9.3 254.2 11.7 267.9 13.7 254.2 8.4 268.8 10.7 282.5 12.9

11.8 13.0 15.3 10.1 12.1 14.8 9.3 11.7 14.0 8.5 10.8 13.8 7.9 10.5 13.0 7.2 10.0 12.4 6.4 9.1 11.7

3214 128.0 2506 134.4 1976 142.2 3078 140.8 2494 149.0 2005 159.1 3110 154.5 2568 164.6 1964 172.8 3122 169.2 2517 179.2 2021 189.3 3144 183.8 2565 194.8 1948 203.9 3118 197.5 2570 210.3 1887 218.5 3071 211.2 2461 222.2 1810 232.3

Dynamic Approx loft driver loft (degree) (degree) 18.5 14.0 10.5 16.5 13.0 10.0 15.5 12.5 9.0 14.5 11.5 9.0 13.5 11.0 8.0 13.0 10.0 7.0 12.0 9.0 6.5

69

How far can a golfer drive the ball (step 2)?

How can I maximize my drive distance?

Step 2: optimizing for launch angle and spin rate In general terms: 1 The lower your club head speed, the more loft you will need for maximum distance, and vice versa.

bowed forward (adding loft dynamically, hence the name), and vice versa. Estimates vary widely as to the maximum amount of loft that shaft bending can add, but 2.5–3.0 degrees seems to be generally accepted.

2 For a given club head and ball speed, as launch angle increases, the spin rate will need to decrease for maximum distance, and vice versa.

7 For a golfer with a late release, a shaft that is stiffer overall and/or has a more tip-stiff bend profile can produce significantly lower launch angles and spin rates, and vice versa.

3 Launch angle is controlled by the loft of the club face at the point of impact (its ‘dynamic’ or ‘effective’ loft), which includes the golfer’s angle of attack. Spin is controlled by a combination of ‘spin loft’ (loft at impact relative to the angle of attack), club head speed and vertical gear effect (see page 89).

8 A golfer with an early release will see less or even no noticeable trajectory change from different shaft flexes or bend profiles.

4 Dynamic loft (also known as ‘effective loft’) is not the same as the stated loft of the club. The latter is the actual loft at address or in a gauge (its ‘static loft’).

9 Dynamic loft can be – and often is­– added by a golfer’s swing mechanics, usually as a result of ‘flipping’ the hands and the club through impact (see graphic on page 73); the reverse can also happen, but only in extremely rare cases.

d Increasing dynamic loft

To maximize the distance of a drive, the golfer has to achieve the ideal combination of ball speed, launch angle and spin rate (below). An increase in dynamic loft (bottom right) will result in an increase in launch angle, but because the ‘spin loft’ (the loft at impact relative to the AOA) has not increased, neither will the spin rate. If the ‘spin loft’ increases, that will raise the launch angle, spin rate and trajectory, which will affect the distance that the ball carries and rolls. These images are adapted from an original conception by TrackMan™.1

5 Angle of attack changes affect launch angle but have little or no effect on the spin rate. Dynamic loft changes affect both launch angle and spin rate. 6 The higher the club head speed and the closer to impact the golfer releases the wristcock, the more the shaft will tend to be

ular pendic r e p ( ) b face e ball the clu act with th f o n p im tatio Orien e point of at th

Ball direction Spin loft

Launch angle

70

The Equipment

Dynamic loft

Angle of attack

Each item a grouped object

10 With drivers only, impacting the ball above the head centre of gravity will reduce the spin rate and vice versa. Step 1 should have determined the combination of club length, shaft, club total weight and ‘swinging balance’ (swingweight or moment of inertia) that provided the best combination of club head speed/ball speed, impact consistency and feel. Some golfers are very sensitive to feeling how a shaft bends during the swing and have distinct preferences for one shaft over another. Since they also tend to be the sort of player for whom different shafts can produce different trajectories and even precipitate unwanted swing changes, establishing the head specifications that will optimize their trajectory is probably best left until last. A If you have gained sufficient experience, as either a clubfitter or player, you will probably know instinctively if the ball flight you see is ‘right’, but if not the data produced by an accurate launch monitor will certainly help to ensure that you get as close as possible to maximizing your potential distance with an acceptable level of accuracy and consistency. Even if a driver head is adjustable, typical manufacturing tolerances mean that there cannot be only very distinct differences between ostensibly identical heads, but also that the various settings will not necessarily correspond exactly to the published specifications. B

d Better balance

These two illustrations demonstrate the importance of a properly balanced and fitted club. The A left-hand image shows the impact pattern (after six shots) with a driver that is too long and the wrong balance for the golfer to control and swing well and consistently. The right-hand image shows the impacts (after ten shots) for the same golfer with the same driver, but this time Each item a groupedcustomized object for the best length and balance.

B

Incorrectly balanced club – impact pattern after six shots

r

la dicu rpen ll) e p ( ba face the club ct with e h ft pa f im ion o ntat point o e i r O e at th

Launch angle (higher)

Correctly balanced club – impact pattern after ten shots

Ball direction (higher launch, same spin) Spin loft (no change) Angle of attack (less downward or more positive)

Dynamic loft (higher)

71

What does the ‘kick point’ reveal about how a shaft will perform?

How does the bend of a club affect my shots?

‘Kick point’ and ‘bend point’ are thought to be reliable indicators of how high (or low) a trajectory the club shaft will produce. They tend to be used interchangeably, although they are measured in different ways: one involves compressing the two ends of the shaft between two steel plates, and the other clamping the butt end of the shaft and deflecting the tip end with a weight. The point of maximum bending is then measured relative to the tip in each case. Neither of these methods of measurement truly reflects how a shaft bends in response to the forces applied during the golf swing – and there are no agreed standards as to what constitutes a high, mid, or low kick point or bend point shaft (just as there are no agreed standards for the various flex designations used by different companies – for instance, L, A, R, S, Regular, Firm or Lite). A much more reliable indicator of the relative trajectories two or more shafts will produce is to compare what is called their ‘bend profiles’ (the way in which the flex of each shaft is distributed along its length), by measuring each shaft’s actual stiffness in either frequency (cycles per minute) or engineering EI units at multiple points along its length. As a side benefit, a shaft’s bend profile will also suggest what swing type it will be likely to suit, in terms of club head speed, backswing to downswing transition (aggressive or smooth), swing tempo (fast or slow) and the release of the wristcock angle (early or late). However, golfers do not generally have access to bend profile data, which are difficult to interpret without quite lot of knowledge, so they still tend to think in terms of kick point or bend point, which are not necessarily reliable indicators of what sort of trajectory a particular shaft will provide, for two reasons: as already indicated, both terms are subjective; and whether or not two shafts with different flex distributions will actually produce visibly different trajectories depends to a large extent on how late or early the golfer releases the club (that is, where the wristcock angle starts to unwind).

72

The Equipment

Typical carbon fibre shaft

Outer layer

Radial or bias plies at 45° to longitudinal shaft axis (to control torque) Layer of proprietary material (optional) Axial plies at 90° to longitudinal shaft axis Longitudinal plies parallel with shaft axis Radial or bias plies at 135° to longitudinal shaft axis (to control torque)

o Controlling torque The early graphite shafts had very low torsional stiffness (high torque), which was subsequently solved by incorporating several layers of ‘radial’ or ‘bias’ plies set at 45 degrees/135 degrees to the shaft axis. By varying the orientation, modulus (strength) and placement of the carbon fibres in the various layers that make up a shaft, its bending and torsional properties can be varied at different points.

Shaft bend profiles and ball flight Higher launch, higher spin shaft

Mid launch, mid spin shaft

Lower launch, lower spin shaft

A

o Trajectories from different bend profiles A

Release

How much trajectory change any golfer will see from shafts with different bend profiles will depend on the club head speed, whether they release their wristcock angle early or late, and how much the bend profiles differ.

B

g Effects of different releases The golfer in the top

B

sequence has an ‘early’ release. He will tend to hit the ball high because he has allowed the club head to get ahead of his hands at impact by ‘flipping’ his wrists and thus adding loft with his swing. He will be unlikely to see much change in his trajectory from selecting a more tip-stiff shaft design. The golfer below has a ‘late’ release. He almost certainly will see different trajectories with the same club head from using shafts with different bend profiles.

73

How is the ‘coefficient of restitution’ measured?

Why is the transfer of energy from club face to ball important?

When a golf club impacts a golf ball, the vast majority of energy lost (as much as 99 per cent, according to some estimates) comes from the ball compressing and deforming against the club face, with the balance being lost to the club head. Using those figures, halving the amount of energy absorbed by the club head would only result in about 0.5 per cent more energy available to be converted to ball speed, compared with almost 50 per cent more energy from halving the ball losses. One way to produce more ball speed and potentially more distance would be to re-engineer the golf ball, but they are subject to an initial velocity limit specified by the rulemakers. However, the combination of bigger driver heads and advances in material technology has allowed the club face to be made thinner and thus flex inward at impact. While that increases the very small amount of energy absorbed by the club head, it greatly reduces the much greater amount of energy lost to the golf ball – and the net result is an increase in the initial ball speed. The United States Golf Association (USGA) considered this development a threat to the integrity of the game and, in 2002, imposed an arbitrary coefficient of restitution (COR) limit of 0.83 on driving clubs with lofts of 15 degrees or less (see caption at top of page 75 for an explanation of COR). Although they initially resisted a similar decision, the Royal and Ancient (R&A) eventually followed suit. In 2006, the 0.83 COR limit was extended to apply to all clubs. How much has imposing a COR limit actually affected driving distance? All else remaining equal, if you have a driver club head speed around 153 km/h (95 mph), the distance you might expect to hit an ‘illegal’ driver with a 0.84 COR is only a Direction of yard or two more than you would get from club head a ‘legal’ driver with a COR of 0.83. travel

However, if you use a non-conforming driver in a qualifying competition, you may or may not be disqualified, depending on how the ‘conditions of competition’ are phrased. There is no requirement for club manufacturers to submit clubs for COR conformity testing, but, if they do, their clubs will be placed on either the ‘conforming’ or ‘non-conforming’ lists of clubs maintained by the R&A and USGA, which you can see on their respective web sites. If the ‘conditions of competition’ state that you must use a driver that is on the ‘conforming’ list, you must use a driver that is on that list, but if they simply state that you may not use a driver that is on the ‘non-conforming’ list, you are free to use any driver that is not on the ‘nonconforming’ list, even if it is not on the ‘conforming’ list, because drivers are presumed to be conforming unless they have been tested for conformity and failed.

Cannon and ball Timing sensor

Timing sensor Air cannon

Loft set to 0° Approach speed measured at 161 km/h (100 mph)

Timing sensor

Timing sensor Air cannon

Exit speed measured at 134 km/h (82 mph)

74

The Equipment

Bouncing balls Solid surface

Impact speed 161 km/h (100 mph) Rebound speed 161 km/h (100 mph) COR = 1

Solid surface

Impact speed 161 km/h (100 mph) Rebound speed 121 km/h (75 mph) COR = 0.75

A simple way to appreciate the concept of COR is to imagine that a golf ball is thrown against a rigid wall at 161 km/h (100 mph) and it bounces back at 121 km/h (75 mph)). The COR is therefore 121/161 = 0.75, that being the exit speed divided by the approach speed.

ga Testing COR and CT The original COR test used an air cannon to fire a golf ball at a known speed at the face of the club head and calculated the COR based on the relative rebound velocities of the ball and the club head (left). In 2004, an alternative ‘CT test’ protocol was introduced for the testing of drivers, using a portable rig in which the club face is impacted by a steel pendulum and the ‘characteristic time’ (the time that the pendulum is in contact with the club face) is measured (right). The CT is directly related to the COR of the club face. However, it has since been determined that CT only correlates with the COR (as measured by the air cannon test) for drivers, so the air cannon test has been reintroduced for club heads other than drivers.

g Coefficient of restitution The coefficient of restitution (COR) is a measure of the efficiency of the transfer of momentum between two colliding bodies – for example, a club head and a golf ball. A COR of 1.0 would mean that no energy at all is lost and a COR of 0.0 that all energy is lost. A COR of 0.830 (the limit imposed by the USGA and R&A on conforming drivers and other clubs) represents a 17 per cent energy loss.

Test rig

This rig was adopted by the R&A and USGA to determine whether driver heads conform to the rules on ‘springlike effect’, using CT (characteristic time) as a proxy for COR.

75

equipment: the iron

At one time, golf clubs were fashioned entirely from wood and animal bone or horn. Since about 1900, the combination of advances in manufacturing, materials technology and club head design have undoubtedly changed the game and how it is played.

Steel shafts began to replace hickory in the late 1920s. Since then other developments have followed, including cavity-backed (perimeter-weighted) irons, hollow-bodied metal woods, graphite shafts, titanium wood heads, hollowbodied hybrid iron replacements (or ‘rescue’ clubs) and the widespread use of investment casting to make iron heads.

All these are grouped individual objects lineones. weights except 1960’s cast ones. All these are grouped as individual objects no lineasweights except 1960’sno cast

The early metal iron heads were often forged by local blacksmiths. Although more durable than their wooden predecessors, the lack of any perimeter weighting, their narrow soles and sharp leading edges made them difficult to use, and they tended to destroy the expensive golf balls, or ‘featheries’ (so called because they were made from leather and compressed, boiled feathers). The evolution of the golf ‘iron’ is shown below. mid 1800’s revised.

d Beginnings

grouped object no line weights

The basic concept of d 1800s The more lofted and a set of clubs with different lengths shorter clubs began to be made and lofts to provide a progression of from iron (hence the name), trajectories and distances was developed by local blacksmiths. The (longer shafts with lower lofts resultones. incast ones. combination of their design and objects s no lineno weights line weights except except 1960’s 1960’s cast lower trajectories and more distance, hickory shafts made them whereas shorter shafts and higher difficult to use in comparison with 16th moderncentury irons. lofts equal higher trajectories and less distance).

76

d Late 1800s to early 1900s The first patent for a metal wood head was taken out in 1896 by Sir William Mills. Face scorelines (grooves) started to replace punch marks on metal iron heads. The first steel shafts were made in 16th century 1893 by Thomas Horsburgh, but were not approved for tournament use until the 1920s.

d 1960s to present Cavity-backed iron heads produced by the investment casting (or ‘lost wax’) process started to be produced. The first carbon fibre shafts appeared in about 1973.

mid 1800’s

mid 1800’s

ntury

Until about the mid-1990s, irons were numbered from 1 to 9 and sold in sets with a pitching wedge and sand wedge. However, this has changed in recent years as the club companies have gradually decreased iron lofts – in some cases considerably. In the 1960s to 1970s, typical lofts for the 4 iron, 6 iron, 8 iron and pitching wedge were respectively 28º, 36º, 44º and 52º, but today you can buy iron sets with 20º 4 irons, 26º 6 irons, 34º 8 irons and 44º pitching wedges.

1902 approx The Equipment

1902 approx

1960’s 1960’s cast these e these each have .2 have .25 outer edge line weight

Iron anatomy Grip Usually made from a rubber compound, but increasingly from synthetic materials, the grip should be customized to fit the golfer’s hands and allow them to hold the club securely with minimal muscle tension in the hands, wrists and forearms.

Weight distribution A rear cavity allows weight to be moved to the heel and toe areas to reduce club head twisting on off-centre impacts. Top edge Centre of gravity

Leading edge

Grooves Combined with face milling, grooves (or scorelines) help to promote spin (mainly from the rough or semirough). In 2010, the USGA and R&A changed the rules to try to limit their effectiveness. Centre line

Loft (°)

Shaft Generally made from steel or carbon fibre composite, the shaft is the main determinant of the weight of the club, and, for a player with a relatively late release of the wristcock angle, can affect the launch angle, spin rate and trajectory of the shot. Hosel The hosel connects the club head to the shaft. Additional weight can be added internally to adjust the club balance (swingweight or moment of inertia). It may also be bendable and so allow the club loft or lie to be adjusted.

Length

Vertical to ground

lan

ft p

Lo e

Lie

90° Horizontal to back edge of the heel

Horizontal to centre Club face Loft and surface roughness affect launch angle and spin. Variable-thickness face inserts made from high-strength, more ‘elastic’ metal alloys can reduce ball speed drop-off and thus provide more consistent distance on off-centre impacts..

Sole The width and profile of the sole (front-to-back and toe-to-heel) affect the way that the club interacts with the turf.

Club head The loft, lie and face angle at impact affect the launch angle, spin, initial direction and shape (hook or draw, fade or slice) of the shot.

o Iron specifications The iron head specifications (loft, lie, sole configuration, offset, weight, weight distribution, centre of gravity location, and in some cases even its appearance at address), in conjunction with the shaft, and the final assembly specifications of the club, will all affect how well the golfer will play with it. 77

What aspects of a golf club affect feel?

What is ‘feel’?

‘Feel’ is how the brain interprets all the various sensations which the nerves transmit to it when a club is swung or strikes a ball. What the golfer’s conscious brain registers and how well or badly those various sensations match their personal preferences will tend to produce a subjective like or dislike of a club. Not all golfers are equally sensitive to the various features of an assembled club that affect feel. Ask one golfer to describe how a club ‘feels’ and the response may simply be ‘nice’ or ‘bad’ – a good clubfitter will need to investigate further to ascertain precisely which aspect of the feel of the club the golfer likes or otherwise. Ask another golfer and you may get instant and detailed feedback on the overall bending feel of the shaft, where in their swing and which segment (butt, mid-section or tip) they could sense bending, the physical weight of the club, its moment of inertia or swingweight, if the impact felt ‘solid’ or harsh, and even grip texture or size. If a golfer feels completely ‘at one’ with a club, they will generally swing it better, and altering certain specifications which affect the feel of a club can produce measurable differences in the way in which a golfer swings it (for example, in their swing path or the release of the club) – even if they have not consciously noticed any real change in the way it feels. Does that mean that ‘feel’ also operates on a subconscious level, or is it simply that the laws of physics have intervened – or a combination of both? There is little doubt that a golfer’s sense of feel – or their sensitivity to particular aspects or combinations of feel – can change over time, even from day to day or hour to hour (try wielding a sledge hammer for 10 minutes and then pick up and swing your driver). ‘Feel’ is subjective rather than absolute, which is why it is a difficult term to define in a meaningful way that applies to all golfers. However, it is clear that a golfer can acquire a better sense of feel over time.

78

The Equipment

Neural feedback ‘What aspects of how this club feels am I sensing?’

Neural signals Wrists and forearms

Shaft overall stiffness and stiffness profile feel

Hands

Club total weight feel and club balance feel Vibration (or ‘impact feel’)

o Sensory perception Most of the sensory feedback which is interpreted by the brain is picked up by the nerves of the fingers, hands, wrists and forearms, because ultimately these are the parts of the body which connect the golfer to the club.

Feel factors Overall stiffness and bend profile Both the overall flex and the flex distribution of a shaft play a part in transmitting the sense of where and when the shaft is bending during the swing, which, for golfers who are sensitive to it, can have a very significant effect on their timing and the freedom with which they sense that they can swing a particular club.

Assembled moment of inertia/swingweight The ‘balance’ of the club (which golfers often describe in terms of the club being ‘head-light/head-heavy’ or of it releasing too early/late or too fast/slowly) is affected by the club weight and balance point in relation to the hands. The same actual moment of inertia or swingweight setting will not necessarily feel the same to all golfers – and different golfers will need different settings to provide the best feel to maintain a consistent swing tempo and time the release of the club into impact.

Shaft flex

Club total weight The physical weight of a club is controlled mainly by the weight of the shaft, which can vary from as little as 40 g to as much as 120 g or more. Standard, mass-produced clubs or sets of clubs tend to be built to standard lengths and swingweights, which does not allow much variation in the weights of the heads. Although weight can be measured, the same club may not actually feel heavy or light to any one golfer unless they pick up a heavier or lighter one.

Club head impact The sensation of the club head impacting the ball is affected by four things: club head design; where on the club face the ball is struck; club head material; the flex and the flex profile of the shaft. While any of those factors can elicit comments such as ‘This club feels soft (or harsh, or “dead”) when I hit the ball’, it is highly unlikely that impact feel can be objectively quantified in a way that is meaningful for all golfers. However, the golf shaft contributes to feel in a number of ways, which is probably why many golfers regard it as the most important component of any golf club.

o How a club ‘feels’ What any golfer feels when they swing a club, and when the club hits the ball, is a composite of a number of different sensations. These are picked up by the fingers, hands, wrists and forearms and then interpreted by the brain. However, one particular aspect – ‘impact feel’ – has been shown to be hugely influenced by impact sound, which the brain subjectively ‘translates’ to impact feel.

79

How does perimeter weighting reduce the effects of imperfect ball striking?

How can club head weight distribution help my game?

The term ‘sweetspot’ is often misused. Strictly speaking, a ball is only truly struck on the ‘sweetspot’ when the force vector of the centre of gravity (COG) of the club head is aligned with the COG of the golf ball – both are simply points in space and cannot be increased in size. In practice, the term ‘sweetspot’ has come to mean something else, namely a significantly larger area surrounding the centre of the face where the ball impact can occur without the player sensing a harsh strike and without it resulting in a significant loss of accuracy or distance. Therefore, the commonly accepted definition of the ‘sweetspot’ is mainly a function of the moment of inertia (MOI) of the club head – so the greater that is, the larger the ‘sweetspot’ will be. When a ball is struck towards the toe or heel of the club head, the club head will twist about a vertical axis that passes through its COG. Shifting weight away from the COG and out towards the outer points or perimeter of the club head (hence the term ‘perimeter weighting’) allows the MOI of the club head to be increased. The bigger and heavier the club head, the greater the weight that is repositioned away from the club head COG; and the further away it is placed from the COG, the higher the club head MOI can be. Drivers – having by far the biggest heads – can have the highest MOIs. Club heads are subject to maximum limits imposed by the rulemakers on both size (460 cc) and MOI (5900 g/cm²) – so club heads cannot be made significantly more ‘forgiving’ than they currently are. Because of the practicalities of building clubs that golfers can swing effectively and comfortably, the sizes and weights of

a Maximizing forgiveness

Various designs of clubs have evolved to increase resistance to twisting and ball speed drop-off on off-centre impacts. Modern methods of manufacture have allowed club designers to position more club head weight away from the centre of gravity of the club, towards the outer edges or sides of the club head, thus increasing the club head’s moment of inertia, and subsequently enlarging the sweetspot on the club face.

80

The Equipment

fairway wood, hybrid and iron heads are pretty much fixed, so they probably cannot be engineered to twist any less for a given off-centre impact than now. So for all clubs – including a few high-tech, multi-material iron heads – the design emphasis has shifted to developing highly engineered, variable-thickness faces made from high-strength steel and titanium alloys which can reduce the amount of drop-off in ball speed and distance that normally occurs with off-centre impacts.

Club head designs and MOIs Blade iron 1000 g/cm2

Shallow-cavity iron 2000 g/cm2

Very large-cavity (or super game-improvement) iron 2800 g/cm2

Reducing the difference

a Differences in impact

The effects on distance of off-centre impacts with different types of iron head, including one with a variable-thickness, high-COR component, which is able not only to flex, but to flex more towards the periphery, where the face is thinner. While ball speed and distance are increased on both on-centre and off-centre impacts, the more flexible outer areas of the face can deflect more and thus maintain more of the ball speed and distance that would otherwise be lost on off-centre strikes, even with a traditional big-cavity iron head. In other words these high-tech heads provide more consistent distance on good and bad strikes.

Blade (muscleback) iron Shallow-cavity iron

Big-cavity iron

Big-cavity iron with a high-COR, variable-thickness face

Ball speed and distance (off-centre impact)

Ball speed and distance (on-centre impact)

Moving the weight

Hybrid iron 2800 g/cm2 Enlarge head front to back and/or heel to toe

150cc fairway wood 3000 g/cm2

Shift weight to periphery of club head, including thicker wall

Add weights inside club 460cc driver 5300 g/cm2 centre of gravity location

o Increasing MOI Three possible methods for increasing a driver head’s moment of inertia using perimeter weighting are illustrated here. All designs provide ways of pushing the weight of the club head back and out, away from its centre of gravity, thus increasing the MOI of the club head. 81

Are club head materials and manufacturing methods significant?

Does how the club head is made affect my golf?

Most iron heads are, broadly speaking, made by one of two processes: investment casting or forging. Investment-cast heads are generally made from stainless steel, but can be made from a number of other metals, including carbon steel (which is then normally chrome-plated to prevent rusting), copper-based alloys and even titanium. Forged irons are usually made by passing a single billet of soft carbon steel sequentially through several dies in a forging press, after which it is handground and chrome-plated. There is a ‘halfway house’ between the two methods (called ‘form forging’ or ‘coin forging’), in which the head is first cast to its basic shape and then finished in a forging press.

backs of the heads. So-called ‘game improvement’ designs are more likely to be cast with large cavities (to maximize perimeter weighting) and other features like wider soles, lower centres of gravity, and more offset to help improve shot outcomes for less skilled golfers by making the clubs more ‘playable’. However, all those things are functions of the head design, not of the manufacturing method or the materials used.

There is no difference in performance (launch angle, spin or distance) between a forged and a cast iron head of the same design. The more skilled the golfer, the less they will need a significant amount of perimeter weighting. Most forged heads tend to be targeted at this group of players, so tend to be less ‘forgiving’ than typical cast heads, but there are some very forgiving forged irons available with large cavities milled in the

Wood heads are made from a variety of materials. Drivers are almost universally made from titanium alloys these days (and are increasingly being fabricated from three to four segments), while fairway woods are still mainly made from stainless steel. Some companies have produced multi-material driver and fairway wood heads mainly to manipulate the club head centre of gravity (for example, lowering it by making the crown of carbon composite and thus influencing launch angle and spin), rather than increasing ball speed, although combining advanced metal alloys and clever face design means that some fairway woods are now pushing up against the 0.83 COR (coefficient of restitution) limit, which previously they could not.

Casting iron heads

Exact wax masters made

82

The Equipment

Wax masters assembled into ‘trees’ with branches that will form channels for molten metal to flow through

Trees then repeatedly dipped in a ceramic slurry. Wax is removed in an autoclave to make a hard casting mould

Molten metal is poured into tree mould

Mould is broken, club heads removed and finished

Driver

Driver heads tend to be made of titanium because they can be made larger and more ‘forgiving’ in off-centre impacts.

Iron If the face area of an iron is replaced with a separate, lighter insert, the weight saved can be moved to other areas to enhance playability and forgiveness.

Titanium or carbon composite crown piece.

Varying the face thickness can reduce distance loss on off-centre hits.

If the face insert is made from a material that allows it to flex and reduces in thickness towards the edges, off-centre impact performance can be improved even more.

Increasing the size (blade length) of a cavity-backed iron head will automatically increase its MOI (moment of inertia), also improving forgiveness.

o Material choices The decision about what material and manufacturing process will be adopted for any club head depends on many factors: required performance and adjustability, production costs and even what golfers expect. While it’s technically possible to cast blade (muscleback) irons from stainless steel and to fabricate driver heads from high-strength steel alloys that are right on the 0.83 coefficient of restitution limit, a set of blades made from anything other than forged carbon steel, or a driver that isn’t made from a titanium alloy, might not be acceptable to many golfers, and thus not sell very well.

the two parts are grouped objects..the casting also a compound fill. refi can re-arrange as required by spread..

g Casting process A golf club consists

Forging an iron head

simply of a head, a shaft and a grip, which are mostly made by specialist foundries, and by shaft and grip manufacturers. They are shipped to plants owned by the club companies whose brand names they bear for assembly into finished clubs. Iron heads are made by casting or forging, with some of the newer ‘high tech’ designs incorporating separate face pieces to enhance performance. Wood heads (not shown) are increasingly being fabricated in three or four segments which are welded together, rather than cast.

Heated and bent steel billet placed in first die

Grouped objects Grouped objects

Fo

Two or more dies progressively form head shape

Rough forged head produced for final grinding, machining and plating

83

SCIENCE

IN ACTION

knowing the distances

Once you have selected your golf clubs to suit your swing style, and then focused on developing consistent, centred contact with the ball, the next thing to work on is understanding your shot distances. Remembering how far you hit the ball with each club – knowing your ‘yardages’ – will help to build consistency. You can calculate your yardage for each club, and for different levels of swing for each club, on the practice range by hitting a dozen or so balls – remember not to overhit so your shots are accurate, reproducible and predictable – and making a note of the average distance the ball travels. You can then use your yardages on the course, in tandem with an accurate estimate of the actual distance to target. Remember to base your club selection on your average distances with each club, and, if in doubt, hit more club rather than less – course designers generally put hazards at the fronts of greens for a reason. Tour pros benefit from the assistance of experienced caddies who provide them with detailed distance information for each shot. Most golfers, however, have to rely on other methods. Golf courses often provide basic information for golfers in the form of course maps with tee-to-hole distances, or distance markers on the course, but new technology is again coming to the rescue. Devices which use a global positioning system (GPS) offer a way of pinpointing the golfer’s position, and the position of the target, to within a couple of metres. Mobile phone apps are available which use the phone’s position and offline data. However, a mobile phone is not always within signal range. Laser-rangefinder devices are also more common today, and these offer another way to estimate distances. Carry distances will change with wind speed and direction, and the total distance – which includes the roll of the ball on impact – will depend on the condition of the fairway or rough. Once you have an idea of the distance, the choice of shot and club – and taking the shot – are still down to you.

84

The Equipment

a Heads together

English golfer Ross Fisher consults with his caddy Adam Marrow. While Tour pros are able to call on the assistance of experienced and knowledgeable course guides, they also need to know exactly how far they will hit each shot with each club, just like the rest of us. Using this knowledge in conjunction with GPS devices, mobile phone apps, laser rangefinders and the humble course map will help take the guesswork out of each shot.

85

How can the ‘smash factor’ be increased?

How can I hit the ball better?

Understanding ‘smash factor’ is important for several reasons. In the first place, it correlates strongly with how solidly the ball has been struck, so provides useful information about the ‘centredness’, ‘squareness’ and consistency of impact. Secondly, it influences the initial ball speed that will be produced with any club at a given club head speed, which has implications not only with respect to the consistency with which distance can be controlled (important on approach shots), but also with respect to the maximum distance that can be achieved with any club (important for drivers).

d Factor formula

With the appropriate equipment, it is possible to measure the necessary inputs to calculate the maximum ‘smash factor’ achievable with a particular club head using the following formula:

SMASH FACTOR = (1 + COR )

cos( SPIN LOFT) 1 + BALL MASS

CLUB HEAD MASS

Where:

Smash factor is simply the initial speed of the golf ball when it leaves the club face divided by the club head speed at impact. The maximum value for an on-centre and square impact for a given club depends on its loft and the coefficient of restitution (COR) of the club face at the point of impact with the ball; the highest values will be seen with low-lofted clubs with faces that are designed and made from materials that allow them to flex – drivers, fairway woods, hybrids and, more recently, some multi-material iron heads. For a typical driver fitted with a head that is right on the COR limit allowed under the rules, a perfect on-centre strike will result in an initial ball speed about 1½ times faster than the club head speed at impact, which gives a smash factor of 1.5. Tour players are able consistently to hit the ball on or very close to face centre with all their clubs, not only because of their level of skill, but also because their clubs are properly fitted for length, weight, dynamic balance, shaft flex and bend profile. The lower a player’s skill level and/or the less well their clubs fit them, the more their smash factors will tend to be sub-optimal; it is not uncommon, for example, to see higher-handicappers using drivers that are longer, or lighter/heavier in terms of total weight or MOI/swingweight, than they can properly control with smash factors close to 1.40, or in some cases lower than that, which will certainly be costing them distance. 86

The Equipment

COR is the coefficient of restitution of the club head Spin loft is the effective loft (or dynamic loft) of the club head at impact relative to the angle of attack Effective loft is the loft of the club head at the point of impact (as measured in a gauge), plus any loft added by shaft bending, plus any loft added by the golfer’s swing mechanics Angle of attack is the vertical (up–down) angle at which the club head is moving at impact, relative to the horizontal; a positive angle of attack means hitting up on the ball, a negative angle of attack means hitting down on the ball Ball mass is the actual weight of the ball in grams (or ounces) Club head mass is the weight of the club head in grams (or ounces). It must be the actual weight of the head as fitted to the shaft to achieve the desired balance at the chosen club length, which may be quite a bit different from the nominal specified head weight.

Club path

a Max smash

The table on the right shows the average club head speeds, smash factors and ball speeds for the Men’s PGA Tour in 2010 – adapted from data collected and analysed by the makers of the TrackMan™ launch monitor.1 While few amateur golfers can expect to achieve the same club head speeds and distances as some of the best players in the world, with proper coaching and clubs that fit their strength, build and swing profile, every golfer should be able to get close to attaining similar smash factor levels. A golfer with a 153 km/h (95 mph) club head speed and a smash factor of 1.40 could expect to get about an additional 9–11 m (10–12 yd) out of their driver from simply improving their smash factor to 1.47. Increasing it from 1.40 to 1.50 could possibly produce as much as 16–18 m (17–20 yd) more. Regardless of the club head speed, the ball will leave the driver face at an average of ~87 per cent of the spin loft at the point of impact ( +/– ~2.5°). Adding or subtracting the angle of attack will give the ball launch angle relative to the horizontal.

Club speed, km/h (mph)

Ball speed, mph (km/h)

180 (112)

266 (165)

Smash factor

Driver

1.49 172 (107)

254 (158)

Number 3 wood

1.48 166 (103)

245 (152)

Number 5 wood

1.47 160 (100)

235 (146)

Hybrid

1.46 158 (98)

229 (142)

Number 3 iron

1.45 155 (96)

220 (137)

Number 4 iron

1.43 148 (92)

212 (132)

Number 5 iron

1.41 148 (92)

204 (127)

Number 6 iron Example: Spin loft at point of impact = 12° and 87 per cent of 12° = 10.5°. For a level (0°) angle of attack, the launch angle will be ~10.5° (~10.5° +/–0°); for a 3° positive angle of attack the launch angle will be ~13.5° (~10.5° + 3°); for a 3° negative angle of attack, the launch angle will be ~7.5° (~10.5° –3°). The diagram below was adapted from an original graphic by TrackManTM.2

1.38 145 (90)

193 (120)

Number 7 iron

1.33 140 (87)

185 (115)

Number 8 iron

1.32 137 (85)

175 (109)

Number 9 iron Dynamic (or ‘effective’) loft is measured relative to the vertical and includes the angle of attack. Spin loft is measured relative to the AOA, so the two are only the same when the AOA is level (0º)

1.28 134 (83)

164 (102)

Pitching wedge

1.30

e club fac Vertical on orientati

n

Ball directio

ft

Dynamic lo

Launch angle Spin loft Angle of attack (level or 0˚)

87

Which design elements of a club head affect distance?

How does club head design help me hit the ball further?

A perfect golf swing should result in the ball being hit on face centre, but only very skilled golfers can do that consistently; most need some help from the club head designer to maximize distance (and accuracy/consistency) when they don’t. As a result, golf club heads incorporate a range of features to improve their playability for different golfer and swing types, helping to offset the effects of poor swing moves and ball striking. So how can club head design affect a golfer’s game? The club head centre of gravity (COG) can affect distance in several ways. Moving the COG location forward or back in relation to the shaft axis can cause more or less forward shaft bending at impact, which – for a golfer with good swing fundamentals – dynamically affects the loft of the club head, but less for irons than for woods and hybrids. Moving it up or down influences launch angle and backspin, but the effect is different

for irons than for woods and particularly drivers. By designing the face so that it can deform when it strikes the golf ball, designers have been able to increase the coefficient of restitution (COR) of the impact between club face and ball, but only up to the current 0.83 COR limit set by the rules. That is only possible for club heads with thin faces made from special high-strength steel or titanium alloys, and not for traditional iron heads, which are cast or forged from a single material. As a result, the current design emphasis is now on trying to maintain the COR as close as possible to 0.83 over a larger area of the face. The loft of the club head, in conjunction with the shaft and the golfer’s swing mechanics, directly affects the vertical angle and the spin rate at which the golf ball leaves the club face. Both need to be optimized if maximum distance is to be achieved

Centre of gravity centre of gravity location Higher COG/Impact below COG = lower launch, higher spin Rearward COG = more shaft bend = higher launch, higher spin

Lower COG/Impact above COG = higher launch, lower spin

88

The Equipment

Loft at face centre

Forward COG = less shaft bend = lower launch, lower spin

ga Effect of COG location Moving the COG location of a large, deep-faced driver head up/down or back/forward can affect ball flight and distance in several ways. If the ball is struck above the COG, the head will rotate backwards, thereby reducing the amount of backspin with which the ball leaves the face (see left) through what is called Vertical Gear Effect (an impact below the COG will increase the spin). If the club face is also made with a top-to-bottom radius (called vertical roll), the greater loft on the upper part of the face will cause the ball to launch higher than it otherwise would, and vice versa (see right). Note that vertical gear effect can be ignored with irons, because the club head COG is much closer to the club face.

with a driver. The combination of launch angle and spin rate that will result in maximum distance is not the same for all golfers; it can and does vary considerably, depending on their club head speed and angle of attack (AOA), which is the angle at which the club head is travelling at impact relative to the horizontal and which can be downwards, level or upwards. While club head mass can affect distance, it can effectively be ignored because – for reasons that would take more space to explain than is available here – it is, and will probably remain, relatively static.

Vertical face roll and vertical gear effect

Loft angle

(MOI) influences distance, because it affects the amount that the head rotates closed (or open) on miss-hits towards the heel (or toe). The higher its MOI, the less it will twist, the more energy is transferred to the ball and the less it will tend to land off-line (and vice versa). However, the rulemakers have imposed a MOI limit on all club heads of 5900 g/cm² – and only drivers, because of their shape and size (which is limited to 460 cc) will ever get close to that.

Head rotates backwards = backspin decrease

Higher impact = higher loft and launch

Area of highest COR

Loft angle

Lower impact = lower loft and launch

o Moment of inertia The club head moment of inertia

Head rotates forwards = backspin increase

o Club head features In order of importance, the main aspects of club head design that affect ball flight and distance for all clubs are loft, vertical club head COG location (left) and club head MOI (above). For woods (particularly drivers), front/rear COG location can play a part, as can designing the club face to flex on impact with the ball and varying the thickness of the face component to maintain ball velocity and distance on off-centre impacts (see above). 89

If mastering the golf swing isn’t hard enough, trying to predict how the ball will move through the air or roll on the green is not just a matter of art, but also one of science. Golf is not played in a vacuum, but rather in a constantly changing environment in which the player and equipment are exposed to a variety of conditions. By applying scientific principles to explain how environmental factors such as rain, wind, temperature or even grass type can influence your score, Andrew Collinson and Sandy Willmott provide answers to some of the more perplexing questions about the impact the environment has on our golf performance.

chapter four

the environment Andrew Collinson and Sandy Willmott

How does the direction of the wind affect the golf ball?

How much distance do I lose into the wind?

Hitting into a headwind or tailwind can be problematic even for the expert golfer. Aerodynamically what is important is the ball’s speed relative to the air rather than to the ground. This speed is higher when there is a headwind, and the drag force on the ball increases – leading to a shorter shot. Perhaps more surprising is that the ball also flies higher because a ball with backspin experiences a lift force due to the Magnus effect (see opposite), and this force also increases as the speed of the air relative to the ball increases. The higher trajectory compounds these effects because the wind speed will typically increase with height, as interaction with the ground tends to slow the air at lower levels.

The speed of the ball relative to the air is lower when it is hit into a tailwind, and the ball will travel further and lower as a result of smaller drag and lift forces. If the ball has sidespin, the Magnus force now points sideways rather than upwards and causes the ball to fade or draw. This force will be larger, and the sideways motion more pronounced, when hitting into a headwind. It is therefore apparent that the main problem with playing into the wind is attempting to predict the effect it will have on the ball. An expert golfer will normally try to minimize the influence that the wind has by reducing the height of their shot. This involves hitting the ball with a lower launch angle and less backspin.

Forces on the ball during flight Lift force

Backspin Drag force

Ball flight

Weight

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The Environment

Air flow

o A real drag The flight of the ball into a headwind will be higher but also shorter than when struck into a tailwind or into still air. This is because of increased lift and drag forces, caused by the increased speed of the air molecules relative to the motion of the ball. A drag force still exists on the ball in a tailwind even though the air molecules are moving in the same direction as the ball. This is because the speed of the ball is greater than the speed of the air molecules, meaning it is still the front of the ball that contacts the air first.

Headwinds and tailwinds

Shot into a headwind

d Into the wind The loss of distance for a shot struck into a headwind is greater than the distance gained for a shot struck with a tailwind of the same magnitude. One factor contributing to this is an increase in the wind speed relative to the ground as the height of the ball increases. Friction between the ground and the air immediately above it means that the wind speed is zero at ground level (the ‘no slip condition’), but increases as the air gets further from the ground’s influence.

Shot into no wind The wind will also influence the roll of the ball when it lands. The higher trajectory of the shot into a headwind will cause a steeper descent of the ball, which will reduce the distance the ball rolls upon landing. With a shot into a tailwind, the distance the ball rolls will increase as the descent of the ball will be shallower.

d Magnus effect As the ball starts to spin, a thin layer of air – the boundary layer – is pulled round with it. When the ball has backspin, the air in the boundary layer is moving against the oncoming wind at the bottom of the ball and with the oncoming wind at the top of the ball. This results in an asymmetric flow with the boundary layer breaking away – or separating – from the ball’s surface further forward on the bottom side (see opposite). The wake behind the ball is deflected downwards, indicating that the ball is exerting a downward force on the air. By Newton’s Third Law of Motion the air in return must be exerting an upward force on the ball, which is the Magnus force.

Headwind Shot into a tailwind

No wind

Tailwind

The effect of spin

Boundary layer

Magnus force Backspin

93

How does water in the air affect the flight of the ball?

Why are my drives shorter in the rain?

It might seem logical to assume that the presence of moisture in the air, be it in the form of raindrops or water vapour, would have a negative effect on the flight of the golf ball, leading to shorter shots. A raindrop hitting the ball will indeed slow the ball down, but by how much? Actually surprisingly little because the magnitude of a raindrop’s momentum – its mass multiplied by its speed – is much smaller than that of the ball’s momentum. A golf ball has a mass of 45.9 g (1.6 oz) and a typical initial speed of 70 m/s (230 ft/s). If an average raindrop has a mass of 0.008 g (0.0003 oz) and travels at 4.75 m/s (15.6 ft/s) then even the worst case of a head-on collision will only reduce the speed of the ball by 0.013 m/s (0.043 ft/s) if the collision between the ball and raindrop is considered to be an inelastic one. If the raindrop’s mass and speed were doubled, the ball would still lose less than 0.028 m/s (0.092 ft/s) per collision.

So even multiple collisions with raindrops during a ball’s flight will not have a significant effect on its trajectory. Increased water vapour in the air actually reduces the density of the air because water has a lower molecular weight than the nitrogen and oxygen it replaces. A reduced air density leads to a lower drag force and increased driving distance. However, rain may reduce driving distances in a range of other ways. It may reduce the firmness of the surface, reducing the roll of the ball upon landing. It will also influence a golfer’s choice of clothing – waterproofs can affect a golfer’s swing, reducing its length and therefore reducing club head speed at impact. Finally, because of the very nature of the formation of rain, the probability of wind is also increased. So although raindrops themselves may not have a meaningful effect on the ball during its flight, it is likely that many other external factors associated with rain will reduce the distance that a player hits the ball.

Moisture matters Dry air

Humid air

g Ball flight An increase in humidity actually increases the distance the ball will travel through the air. This is because the relative molecular weight of water vapour (H2O, 18) is less than that of the other molecules that make up the composition of the air – mainly nitrogen (N2, 28) and oxygen (O2, 32) – therefore reducing the air’s overall density. A lower air density results in a lower drag force (but also a lower lift force on the ball, which will counteract some of the gain from the lower drag). Ball flight Drag force Gases in dry air Water vapour

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The Environment

Rain effect

Need to know The reason the ball will travel further in humid air can be demonstrated by the formula for drag:

FD = ½ ρv 2 CD A where FD is the drag force, ρ is the density of the air, v is the speed of the air relative to the ball, CD is the drag coefficient, and A is a reference area describing the size of the ball. As CD and A will remain the same and ρ will be smaller in humid air, FD will also be reduced for any given v.

Golf ball mass = 45.9 g (1.6 oz) Golf ball speed = 70 m/s (230 ft/s) Momentum = 3.2 kg m/s (23 lb ft/s)

Raindrop Mass = 0.008 g (0.0003 oz) Speed = 4.75 m/s (15.6 ft/s) Momentum = 0.00004 kg m/s (0.0003 lb ft/s)

Raindrop mass = 0.008 g (0.0003 oz) Raindrop speed = 4.75 m/s (15.6 ft/s) Momentum = 0.00004 kg m/s (0.0003 lb ft/s)

od Drop in the ocean The effect that a raindrop will have on the golf ball during its flight is insignificant. The mass and speed of the ball are considerably greater than those of the average raindrop. If the mass and speed of a golf ball are 45.9 g (1.6 oz) and 70 m/s (230 ft/s) respectively and the average raindrop’s mass and speed are 0.008 g (0.0003 oz) and 4.75 m/s (15.6 ft/s) respectively, then the ball will only be slowed down by 0.013 m/s (0.043 ft/s) in a head-on collision with a raindrop. Despite the fact that there may be multiple collisions during its flight with individual raindrops, the speed of the ball and therefore the distance it travels will hardly be affected.

Ball Mass 45.9 g (1.6 oz) Speed 70 m/s (230 ft/s) (off club) Momentum 3.2 kg m/s (23 lb ft/s)

95

How does the air temperature affect the distance of a drive?

Why do driving distances increase in warm weather?

The majority of golfers will know that the ball travels further on a hotter day, but why does this happen? Changes to the ball’s initial speed and to the aerodynamic forces it experiences are involved. Firstly, the impact between the club face and ball will become more ‘elastic’ at higher temperatures, leading to less energy loss and a higher ball speed. Secondly, the molecules in the air have more kinetic energy at a higher temperature and this results in a lower air density – there are fewer molecules in a given volume. Lower air density leads to less drag on the ball, and an increase in drive distance. However, the lower air density at higher air temperatures will also have the less desirable effect of reducing the lift force on the ball, which will tend to decrease the distance the ball travels (in turn reducing the gains in distance arising from the lower drag). Generally, the ball will travel further through the air when the temperature of the air is increased, but calculating the precise effect that changes in temperature will have on driving distance can be

complicated as this depends on the launch speed, launch angle and spin rate – which will vary for each player. If you normally play where the air temperature is fairly consistent then accounting for changes in air temperature may not be necessary. However, changes in air temperature from day to day or even hour to hour will affect driving distances and club selection on approach shots: teeing off during the warmest part of the day – which is usually in mid- to late afternoon – may add a few yards to your driving distance.

d Energy loss During contact between the club face and the ball, the ball compresses and then regains its original shape. The energy returned during the expansion is always less than the energy required for the compression; some energy is lost as heat and sound. The coefficient of restitution for the collision is a measure of the ratio between the speed at which the ball and club separate after impact and the speed at which they approach (i.e. the club head speed), and it increases with a rise in ball temperature.

Making an impact

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The Environment

Drag force

g Reduced drag

An increase in air temperature has the effect of reducing the density of the air (its mass per unit volume). This reduction in air density therefore reduces the drag force (indicated with red arrows) experienced by the ball during its flight, increasing the distance it will travel.

Ball flight

Need to know The relationship between air density, pressure and temperature can be represented using the formula:

P RT

ρ =

Ball flight

Drag force

where ρ is the density of the air, P is the air pressure, R is the gas constant for dry air and T is the absolute temperature (i.e. in kelvins rather than degrees Fahrenheit or Celsius) of the air. So if P and R stay constant and T increases, then ρ (the air density) will decrease.

Ball flight direction

Warming up

a Increased distance

320 311 302 293 Carry distance (m)

An increase in air temperature will typically have the effect of increasing the distance that a golf ball travels through the air – although the exact magnitude of this effect will depend upon the specific combination of launch speed, launch angle and spin rate. The graph here shows the effect of varying air temperature for three simulated drives1 with different combinations of these three factors.

284 274 265 256

Simulated drive – initial ball speed 295 km/h (183 mph), launch angle 13°, backspin 2140 rpm Simulated drive – initial ball speed 256 km/h (159 mph), launch angle 13°, backspin 2584 rpm Simulated drive – initial ball speed 261 km/h (162 mph), launch angle 9°, backspin 2475 rpm

247 238 229 –18 5 10 24 38 52 Air temperature (°C)

97

How does the landscape affect wind on the golf course?

Why does the direction of the wind change from hole to hole?

Judging the speed and direction of the wind on the golf course can be difficult even for the most expert of golfers. Wind speed typically increases the further you are from the surface of the Earth – as a result of the reduced effect of friction with the ground. Closer to the surface, the natural landscape and terrain will change both the speed and direction of the wind. Trees on the course will further affect these properties of the wind in a complicated manner that depends on factors such as their number, height, shape and spacing.

A golfer may be forgiven for thinking that judging the wind on a links course should be a lot easier than on a parkland course. Although there may be fewer trees on a links course, the natural terrain on this type of golf course may also influence the speed and direction of the wind. The sand dunes found on links courses will cause the speed of the wind to be greater on top of a dune than in front it.1 However, there will also be a turbulent region directly behind the dune. Attempting to predict the speed and direction of the wind in this situation again becomes very difficult. Even the grandstands found at golf events will cause the speed and direction of the wind to change, funnelling the wind through any gaps between them as in a tunnel. This effect may, of course, be largest at the most important – and thus popular – holes.

It’s little wonder that golfers find it very difficult to judge the wind on holes such as the 12th at Augusta National. Anecdotal evidence from professional golfers suggests that the flag stick can be moving in one direction on the 12th green, and yet in a completely different direction on the 11th green – a mere 50 yd (46 m) away. Attempting to judge the wind from the flag stick or by throwing grass into the air on a tree-lined hole becomes almost redundant, as this will not indicate the speed and direction of the wind above the tree line. Analysing the movement of the clouds is a more valid method of determining the wind, as its speed and direction will normally be more consistent above the tree line.

direction of the wind are influenced by the landscape, and trees are often a major component of the landscape on a golf course. The presence of trees will normally have the effect of slowing down the wind, up to and above the height of the trees, although the exact nature of their influence on the wind can be hard to predict. The shape, number and spacing of a given set of trees will all influence the wind speed profile behind them.

98

The Environment

Height above ground

a Factors influencing the wind The speed and

Gone with the wind

Wind speed behind trees

Grandstand effect

o Turbulent air flow The complexity of the air flow on a green surrounded by grandstands means it will be very difficult for a golfer to judge the wind’s effect on a shot into that green. There are multiple factors which will change both the local speed and the direction of the wind. The speed will increase as the wind is

channelled between two grandstands. The speed will drop again as the space opens out over the green, but the flow pattern may become very complicated with localized vortices. Moreover, this pattern will be constantly changing as the direction and strength of the incoming wind varies.

Over the hills

g Hills and ridges

The speed of the wind can also be affected by hills and ridges on the golf course, with the air being accelerated as it is forced up and over a ridge. On the downwind side of the ridge the air flow will be more turbulent, introducing greater variability into the wind direction and speed.

99

equipment: the ball

There is an extraordinary amount of theoretical physics underlying the action of the humble golf ball. The design of the ball, however, came about as a result of the observations of nineteenth-century golfers rather than theories about putting feathers inside a leather casing. From around 1850, cheaper balls began to be used made from gutta-percha – a natural latex made from the sap of varieties of trees in southeast Asia. It was noticed that these balls flew further when the smooth surface had become roughened by play, so players began deliberately to roughen the surface of their ‘gutties’. It was not long before manufacturers were producing balls with rough surfaces, leading to the dimpled balls of today. But it was a long time before the theory caught up with the practice, and offered an explanation for why the dimpled ball went further. Wood 14–17th century

Featherie 17–18th century

A ball travelling through the air will create a high-pressure area on its front side, with air flowing smoothly over its contours. But the air closest to the ball’s surface – the boundary layer – separates from that surface further back around the ball, generating a turbulent wake where the pressure is lower. The pressure difference across the ball causes drag. Dimples on the ball introduce turbulence into the boundary layer itself, which actually helps to delay its separation until a point further downstream on the ball’s rear side. This decreases the width of the wake and, therefore, the pressure differential across the ball. As a result, a dimpled ball has about half the drag of a smooth ball. There is another twist that explains a further benefit of dimples – one that involves the effect of an additional force created by a ball with spin. A smooth ball with backspin generates lift by distorting the air flow so that the ball acts like an aeroplane’s wing. The spinning action results in the air pressure below the ball being higher than the air pressure above it; this imbalance creates an upward force on the ball.1 This phenomenon is enhanced with a dimpled ball, and the result is an increased lift force, as shown in the graph opposite.

History of the golf ball Solid gutta-percha 1850s Haskell ocobo ca. 1890

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The Environment

Bramble ca. 1900

Modern round dimples

Latest hex dimples

Ball flight Air flows around ball smoothly

Smooth ball Wake

Wider vortices create greater drag

Lift force (N)

1.36

0.91

0.45

Dimples create a thin layer of turbulence holding air to the ball

0.0

these are now individually grouped objects... 59.1 118.1 177.2 236.2 295.3

Flight speed (km/h) Golf ball Narrower vortices create less drag

o Point of separation

Dimples on the ball’s surface cause localized turbulence in the boundary layer next to the surface. This helps to stabilize the boundary layer, and the point at which separates from thegrouped surface ofobjects... the ball is located these areit now individually further back around the surface of the ball than it would be for a smooth ball.2



Dimpled ball



Smooth ball

Spin rate = 3000 rpm

o Lift forces

Measurements carried out in a wind tunnel3–5 have shown that, at identical spin rates (a typical value for the first part of a drive), the lift forces Liquid core generated on a smooth ball and on a dimpled golf ball are different. As illustrated in the graph, the smooth ball doesn’t create as much lift as the dimpled one, but it does create some – equivalent to about a third to a half of its own weight for much of the speed range. So it is really the spin that creates the lift – a non-spinning dimpled ball generates no lift – but dimples intensify this effect, helping to optimize a golf ball’s aerodynamic performance.

Types of golf ball

Liquid core

Multilayered

o Liquid centre A small rubber or

o Multi-layered A solid rubber or plastic o Wound core

plastic core is filled with liquid, then rubber windings are tightly wrapped around the core. Coverings such as balata, urethane or elastomer offer higher spin rates and better hold on the greens.

core is surrounded by a urethane-based layer. This in turn is encased in a cover material, which varies from brand to brand. Core size and stiffness dictate the ball’s firmness, durability, distance and spin.

Multilayered

A large solid rubber or plastic core is surrounded by a thin layer of rubber windings tightly wrapped around it. Wound-core balls offer golfers more spin, but they lack the durability and distance of other types of balls.

Solid core wound

o Solid core Constructed with a solid rubber core, surrounded by a single layer, the ball is typically covered with urethanes or ionomers. This type of ball is known for its durability, distance and reduced spin due to its dense construction. 101

What factors affect the amount of spin produced from a bunker shot?

Why does my ball not check from the bunker? Club face forces

The ability to control the distance that the ball will roll when playing from a greenside bunker can be a valuable asset in a player’s short game, and being able to give the ball an appropriate amount of backspin is vital. A parallel, frictional force exerted by the club face on the ball during impact generates the backspin, and this is helped by the grooves on the club face. When hitting from a bunker both this parallel force and the normal force become attenuated as they pass through the sand, and the resultant ball speed and backspin are reduced. However, having a very thin layer of sand between the ball and club face may actually increase the amount of backspin produced, because the sand may act like a strip of sandpaper on the club face. The maximum amount of friction that can be produced is proportional to the coefficient of friction, which would typically be about 0.1 at impact with no sand but can be 1 or more for sandpaper. The type of sand in a bunker can affect the depth to which the ball will plug. Analysis of the sand particles at four famous golf clubs showed that the ball was more likely to plug in the bunkers at Royal St Davids in Wales than in the bunkers at St Andrews in Scotland, due to the smaller average size of the sand particles at the latter course.1,2 The ball was also less likely to plug in the bunkers at Killarney Golf Club and Moortown, as their bunkers contained a greater variation of sand particles.1,2 So, the type and condition of the sand will affect the lie of the ball in the bunker. Understanding how such variables influence the spin rate of a shot from a greenside bunker should improve a player’s short game ability. Hence, if a player is in a plugged lie they will know that the increased amount of sand between the club head and the ball will not only reduce the club head speed but also the ball speed and amount of backspin generated.

102

The Environment

Need to know The maximum amount of friction that could be produced can be quantified using the formula:

Ff = μFn

Normal force

Friction force

where Ff is the frictional force produced, μ is the coefficient of friction (describing the interaction between the two surfaces that are in contact), and Fn represents the normal, or perpendicular, contact force.

o Forces

The club face exerts two forces on the ball during impact. Firstly, a normal force acts at 90 degrees to the club face. Secondly, as the ball tries to move up the club face, a frictional force is generated to oppose this motion. The frictional force generates a torque about the centre of the ball and results in the ball having backspin.

Plugging

Coarse sand

Fine sand

o Sand consistency Research has shown that raking the bunker actually increases the plugging depth of the ball. Increased moisture content, however, will reduce the depth at which the ball will plug.2 Plugging depth increases when the sand is coarse, the sand is uniform, and/or when the sand contains a large number of spherical particles.2

Hitting out of sand

d Shear forces The forces applied by the club face set up shear forces within the sand. Energy is lost and the forces exerted by the sand on the ball in both directions – parallel and perpendicular to the club face – are smaller than those originally made by the club face on the sand. The ball ends up with a lower speed and less backspin than if there had been direct contact between the club and ball. As the layer of sand gets thicker, these effects become even more pronounced.

Less energy dissipated by the sand

Larger forces on the ball

Higher speed and more backspin

More energy dissipated by the sand

Smaller forces on the ball

Lower speed and less backspin

103

How does the lie affect the spin on the ball?

Why doesn’t the ball have backspin from the rough?

Predicting the way that the ball will fly and behave on landing when struck from the rough can be difficult, even for the most expert golfer. This is because the golfer cannot be sure of the effect that the rough grass will have on both the normal contact and frictional forces at impact. A large amount of grass will significantly reduce the normal contact force and the frictional force – with the latter decreasing the backspin produced. A study has shown that, for a 5 iron, the amount of backspin produced from the rough was on average 36 per cent lower than for a shot from the fairway.¹ The reduced backspin will cause the ball to travel further on landing although the reduced normal force at club/ball impact will have caused the launch speed and carry distance to be reduced. It can be surprisingly difficult, even for the expert golfer, to judge the distance of a shot when there are only a few blades of grass between the club head and ball at impact. Despite the normal contact force remaining similar to what they may expect from a shot from the fairway, the reduced

frictional force will cause the ball to travel further on landing (because a reduced frictional force will result in less backspin). This reduction in backspin only occurs for the shorter ironed clubs.² So, theoretically, striking a long iron from the light rough should yield the same results as striking a shot from the fairway – as a long iron club will create less backspin compared with a short iron, even from a fairway lie. Interestingly, many amateur golfers actually prefer to strike the ball from the semi-rough rather than from the fairway.³ The exact reason for this remains unclear; however, the increased margin for error that this lie offers – often the ball will be sitting on top of the semi-rough – may increase the chances that an amateur has for correct ball contact (akin to striking the ball from a tee). Conversely, a professional golfer will always prefer to strike the ball from a ‘tight’ lie as found on the fairway – as they are more proficient at making correct contact with the ball compared with amateurs, and this type of lie enables them to better predict the amount of backspin produced.

A good lie?

a Semi-rough strikes

Research has shown that many amateur golfers actually prefer to play an iron shot from the semi-rough as opposed to a fairway lie.³ Further analysis reveals that amateur golfers also launch the ball higher and produce more backspin from a semi-rough lie compared with a fairway lie. As well as preferring to hit the ball from a semi-rough lie, amateurs also perceived themselves as striking the ball better from this type of lie compared with a fairway lie.3 Fairway lie

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The Environment

Semi-rough lie

Rough forces

g Thick rough When the ball is struck from the rough, both forces on the ball at impact – the normal contact force and the friction force – are altered. When there is a large quantity of grass between the club head and the ball, the contact force will be reduced, meaning the ball will not fly as far in the air. The frictional force and the associated torque about the centre of the ball are also reduced, and the backspin produced will be less than for a shot from the fairway. Consequently, the ball will fly lower and also run further than when the ball is struck from the fairway.

1A

Graphic 1 B a Short rough When there is only a small amount of grass between the club head and the ball at impact, the effect on the normal contact force will be negligible. However, the grass will reduce the frictional force significantly, reducing the backspin produced – although this only occurs for the shorter iron clubs. The flight of the ball will therefore be similar to that from the fairway, although slightly lower, but the ball will run further on landing.

Types of grass

1B

a Grass differences The type of grass found in the rough will also affect the normal contact force produced at impact. Bermuda grass has, on average, a greater volume per leaf than Poa annua grass. Therefore the normal contact force will usually be less at impact when striking from Bermuda rough than from Poa annua rough – meaning the ball will typically fly a shorter distance from Bermuda rough than from Poa annua.

Bermuda grass

Poa annua grass

105

What factors affect the bounce of the ball?

How can I predict the bounce of the ball on the green?

The bounce of a ball when it lands on the green or the fairway will be influenced by two forces made on it by the ground: the normal contact force, which is perpendicular to the surface of the ground, and the frictional force, which acts parallel to the surface. Factors such as the angle of ball descent, the slope of the ground, and whether the green is elevated or depressed, will influence how the ball reacts on the surface on its first bounce. The angle at which the ball descends will influence both the frictional and normal contact forces on the ball at ground impact. A steeper angle of descent will increase the normal force on the ball, increasing the steepness of its rebound angle and decreasing the run on the ball. The angle of descent may also cause the type of friction that is applied to the ball to differ. At moderate to large angles between the path of the ball and orientation of the ground the ball will be subject to static friction from the ground at impact. If this angle gets too small, the ball may slide during its contact with the ground and the friction will be of the sliding (or kinetic) type. Factors influencing the angle of descent of the ball include the club head speed at impact and the type of loft on the club: greater club head speed and a more lofted club will cause the descent of the ball to be steeper. The angle of the surface will also influence the rebound angle of the ball: the ball will rebound more vertically if the slope is tilted towards the golfer, and more horizontally if the slope is tilted away from the golfer. An approach shot to an elevated green will carry a shorter distance than one to a depressed green because the ball is in the air a shorter time, but it will bounce a greater distance horizontally because it will impact at a shallower angle. These effects will be exaggerated for shots hit on a lower trajectory compared with those hit on a higher trajectory.

106

The Environment

Green height

The ball will carry a shorter distance, but bounce a greater distance on an elevated green

High trajectory Low trajectory

A shot at a higher trajectory will carry through the air further but bounce less upon landing compared with a shot struck at a lower trajectory

The ball will carry further through the air but bounce a shorter distance on a depressed green

o Shot distance The distance that the ball flies and bounces/rolls on landing will be affected when hitting shots to elevated and depressed greens. On average, for a 9-m (10-yd) depression, a change to the next club with greater loft is required whereas for a 9-m elevated green, a change to the next club with less loft is required.1 The influence of green height varies with the trajectory of the shot. The effect of relative green height on flight and bounce/roll distance will be greater for a shot with a shallow descent angle than for one with a steeper descent angle.

Flight and bounce 55 m/s (180 ft/s) club head speed 35 m/s (115 ft/s) club head speed

o Drive speed and trajectory The speed of the club head at impact will influence d Impact angle The angle of bounce of the ball on the green will be affected when the angle at which a golf drive descends to the ground. For a drive struck at 35 m/s there is a slope. When the ball lands on a green that slopes towards the golfer, the bounce (115 ft/s) the ball descent angle will be shallower than for a drive struck at 55 m/s of the ball will be more vertical than for a green with a level surface. Alternatively, when 2 (180 ft/s). This change in the angle at which the ball impacts the ground contributes to the ball lands on a green that slopes away from the golfer, the bounce of the ball will be more horizontal than for a level green. This will cause the ball to stop sooner on a green an increased roll of the ball for a drive hit with a slower club head speed. Ball impact that slopes towards the golfer and travel further on a green that slopes away from the angle also changes when different iron shots are struck. 2 The impact angles of shorter dashed line 0.5p ball outline 1pt blue path line (optional) 0.5pt large blue direction arrows 4pt golfer, even before the differing effects of gravity in the two situations are considered. irons are greater than for longer irons – as balls hit with short irons fly shorter but higher However, the relationship between the angle of the slope and the angle at which the ball and descend at a steeper angle. This results in the roll of the ball after ground contact bounces is not a simple one: as the ball deforms the surface slightly it receives a contact being less for the shorter irons than for the longer irons.2 force from the ground that is distributed over a curved contact area.2 Predicting the bounce angle is further complicated by the fact that the ball will deform the surface to a greater extent when landing on an uphill slope than on a downhill one. GRADUATED 108-109 Graphic 2 a

Bounce on slopes

Contact force

108-109 Graphic 2 b

Contact force

107

SCIENCE

IN ACTION

considering the conditions

As we have read, cold, wet and windy conditions can affect the flight and travel of a golf ball. They can also affect the golfer: low temperatures can make muscles tight and more prone to injury, and rain and wind will impact on a player’s concentration and mental endurance. Exposure to cold environments provides significant physiological and psychological challenges for the body.1 In addition to the potentially harmful consequences of such conditions on core body temperature, fatigue, dehydration and poor peripheral circulation can ensue.2 All these factors can dramatically affect a golfer’s performance on top of extreme weather conditions, such as buffeting by high winds. The wind chill index illustrates the cooling effect of wind. Even when air temperatures are high, a cooling breeze can lower body temperatures significantly. Air currents on a windy day magnify heat loss as the warm insulating air layer that surrounds the body is continually exchanged with colder ambient air. For example, on an exposed tee, the ambient temperature of 4°C (40°F) combined with a 32 km/h (20 mph) wind will produce a wind chill temperature of 0°C (32°F). Walking at a quick pace (8 km/h or 5 mph) into the breeze, the wind speed increases to 37 km/h (25 mph), lowering the wind chill temperature further to below freezing.3 It is therefore important to consider ways of combatting the effects of thermal stress on the body by wearing clothing made from microfibre fabrics, and other materials such as Gore-Tex®, which keep the body warm and also allow freedom of movement. Well-placed vents can also be unzipped to allow air to circulate when the body temperature rises. A lot of heat is lost through your head and neck, so wearing a hat is important. Finally, by ensuring you take on adequate nutrition, and plenty of fluids, rounds of golf in the wind and rain can be as productive as summer sessions – if you are motivated enough to go out in the cold weather!

108

The Environment

a Rain man

Playing a round of golf in the rain, wind and cold can be exhilarating, but it can quickly become a test of endurance, particularly if you are not wearing the right clothes. Here Gary Wolstenholme wears layers, including a comfortable, flexible, waterproof and breathable jacket and non-slip rain gloves.

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Do the grass and subsoil of a green affect backspin?

Can I stop the ball on the green?

Amateur golfers are often amazed when they see professionals land iron shots that check suddenly on the green. This amazement will then be followed by the question, ‘Why can’t I do that?’ The most likely explanation can be found in the difference between how professionals and amateurs strike the ball – professionals are able to produce more backspin. However, the greens that most amateurs regularly play on may also reduce their chances of stopping the ball quickly. Research has shown that greens with a higher percentage of sand, together with a lower percentage of moisture, in their subsoil will allow the ball to retain more of its backspin after it makes initial contact with the green.1 Sandy subsoil and low moisture content of a green go hand in hand – a sandy subsoil allows more water to be drained than a clay subsoil would, for

instance. Drier green conditions reduce the depth of the pitch mark when the ball makes initial contact with the green, thus enabling the ball to retain backspin. Yet the reduced depth of the pitch mark also has its drawbacks, primarily increasing the distance the ball travels on its first bounce. The greens found on links and heathland courses facilitate the retention of backspin. The subsoils for both types comprise mainly sand, often due to their proximity to the sea. The greens on moorland and parkland courses contain lower levels of sand in their subsoil. Consequently, the average moisture content of greens on links and heathland courses is lower compared with moorland and parkland courses.2 So an approach shot will stop on an inland course primarily due to the steep rebound angle created by the deep pitch mark, whereas an approach shot onto

Deep pitch mark

g High moisture/Poa annua content

Less forward momentum and less or no backspin retained

If the ball lands on a green with a high moisture and Poa annua grass content, then it is likely to create a deep pitch mark. This deep pitch mark has the effect of rebounding the ball at a steeper angle on its first bounce, reducing the ball’s forward momentum, and causing it to stop more quickly.1 It also removes any backspin that was originally on the ball, meaning the ball will not spin back on the green.

a Low moisture/Poa annua content

A reduced amount of moisture in the green’s subsoil and Poa annua on its surface will reduce the size of the ball’s pitch mark upon green impact. This will cause the ball to bounce at a shallower angle and retain more of its forward momentum. However, reduced depth of the original pitch mark also enables the ball to retain much of its backspin – indeed, if the ball had enough backspin, it would spin back on the second bounce, but this is very rarely achieved.1

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The Environment

Grass and subsoil content Moorland Poa 71%, RGC 29% Sand 58%, Other 42%

a seaside course will stop only if there is enough backspin on the ball. So it could be argued that the capacity to stop the ball on a links or heathland green is the true test of a player’s ball-striking ability. On a links course, only professionals and players who strike the ball correctly and with enough club head speed will be able to generate the required amount of backspin to stop the ball quickly. But while they can stop the ball, even professionals will only very rarely be able to make a ball spin back on a links green. This is because the firmness of links greens reduces the rebound angle of the ball – leaving the ball with more forward momentum than the backspin can counteract.

Shallow pitch mark

Parkland Poa 63%, RGC 37% Sand 72%, Other 28%

Heathland Poa 58%, RGC 42% Sand 85%, Other 15%

Links Poa 58%, RGC 42% Sand 82%, Other 18%

Poa annua grass content

Sand content

Remaining grass content (RGC)

Other (clay, organic matter etc.)

o Green, green grass The subsoil and grass content of greens can vary depending on the location of the golf course. Greens on links and heathland courses will normally contain a lower percentage of Poa annua grass but a higher percentage of sand in their subsoils compared with moorland and parkland courses.2,3

More forward momentum and backspin retained

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What forces affect the roll of the ball on the green?

Why does the ball run further on some greens than on others?

The forces exerted on a rolling ball are actually quite complex. The translation and rotation of the ball will be influenced by gravity, the normal force, kinetic friction and/or the rolling resistance. Typically, once the golf ball leaves the putter face it will initially translate (or skid) across the surface. During this phase it will be subjected to kinetic or sliding friction which will oppose the motion of the ball. This will slow the centre of mass and also create a torque, or turning force, about the centre of mass, and this in turn will start the ball rolling. The ball will be considered in a state of pure roll when the contact point on the ball is moving backwards relative to the ball’s centre of mass at the same speed as the centre is moving forward. On a sloping green, gravity will cause a downhill putt to roll further and an uphill putt to roll shorter. The effect of gravity on the putt will be dictated by the steepness of the slope. Research has also suggested that downhill putts are more likely to stay on line than uphill putts and that this is accentuated on faster greens1 – although, because of the effect of the slope, the ball is likely to travel further past the hole if the putt is missed when putting downhill.

Other variables that can influence the rolling distance of the ball on the green include the mowing height of the grass, the type of grass on the green and the frequency with which the green is irrigated. A greater mowing height, a coarse grass type and a higher moisture level will all increase the frictional force exerted on the ball, which in turn will reduce its rolling distance.

d Gravity and slope

A ball will roll further on a downhill slope than on level ground because the ball’s weight, W, contains a component Wp that is parallel to the direction of the slope and tends to accelerate the ball downhill (a role in which it is opposed by the frictional force Ff ). The magnitude of Wp can be calculated using the formula: where θ is the angle of the slope Wp= W sinθ relative to the horizontal. The larger this angle the greater the value of Wp and its acceleratory effect. If the ball is instead rolling up a slope then Wp and Ff both point down the slope, acting together to decelerate the ball.

Effect of gravity on the ball Fn

Fn

Wp

Wp Ff = frictional force made by the ground on the ball Fn = normal contact force made by the ground on the ball W = weight of the ball Wn = component of weight normal to the slope Wp = component of weight parallel to the slope θ = angle between slope and horizontal

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The Environment

Ff Wn

Ff Wn

W

θ

W

θ

Spring Mowing height 50%

a Friction from grass

Course management and environmental factors will also influence the distance the ball will roll on the green.² The most significant of these is the mowing height of the grass, as a lower mowing height reduces the friction acting on the ball. Mowing height accounts for 75 per cent of the variation in the ball roll distance that arises from environment and course management factors in the summer. However, this influence is reduced to 50 per cent in the spring.² Conversely, irrigation frequency is more important to the distance the ball rolls during the spring (24 per cent) than it is during the summer (9 per cent).² The proportion of nitrogen in the green also has an effect on the distance the ball will roll on the green during the summer but not during the spring. It has been speculated that low nitrogen rates may inhibit the leaf growth required to repair pitch marks, creating an uneven surface where the ball will bounce to a greater extent, reducing the distance the ball rolls.²

Remaining factors 26%

Irrigation frequency 24%

Summer Mowing height 75%

Nitrogen 11%

Remaining factors 5% Irrigation frequency 9%

Roll of the green

g Types of grass The type of grass used on the green will affect the distance the ball rolls. From an analysis of five different types of grasses, the species that was shown to allow the furthest ball roll was Festuca rubra ssp. Litoralis. The grass species that was shown to produce the least ball roll was Poa annua. This was the case for both wet and dry conditions.3

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How do altitude and latitude affect the golf ball?

Where could I go to hit the longest drive?

A golf ball’s path is affected by aerodynamic and gravitational forces during its flight. The influence of both types of force is dependent on location. For instance, a golf ball will fly further at higher altitudes because of a reduction in both aerodynamic and gravitational forces. The drag force will be smaller because the air density is lower at higher altitudes, and drag is proportional to air density (see Need to Know box on page 95) The lower air density also results in less lift force being generated but the latter’s detrimental effect on driving distance is usually smaller than the gain from the reduced drag. The decrease in gravity with increasing altitude might be more surprising. It is a common misconception that the force of gravity is constant on Earth. The gravitational force between two objects is influenced by the mass of the objects (in this instance the Earth and the golf ball) and the distance between them. The mass of the golf ball and the Earth are constant so the force of gravity will depend on the distance of the ball from the centre

of the Earth. By definition, gaining altitude takes you – and your ball­– further from the centre of the Earth, so the influence of gravity will be lower. The force of gravity also varies with latitude. The surface of the Earth is actually 21 km (13 miles) further from the centre of the Earth at the equator than at the North and South Poles. This difference arises from the spinning of the Earth around its central axis. The spinning creates forces that over time have changed the shape of the Earth from a sphere to an oblate spheroid, creating a ‘bulge’ in the Earth’s structure at the equator. Therefore, the ball will fly further at the equator than at the two poles because the distance between the ball and the centre of the Earth is greater – and the resulting gravitational force is smaller at the equator. So what are the implications of this for golf? If you want to increase your driving distance then you should play on a golf course that is at a high altitude and as close as possible to the equator.

Longest drive

g Effect of surface

Fairway grass

Concrete surface

Officially, the longest ever drive on a golf course was struck 471 m (515 yd) in 1974. However, longer golf drives have been hit on airport runways, where the surface is concrete, and even further on ice. This is because the ball will travel further once it has landed on concrete and ice than on the grass of a fairway. When the ball bounces it will lose less of its energy (due to a higher coefficient of restitution) on concrete and ice than on grass. After the ball has stopped bouncing, the reduced deformation of concrete means the rolling resistance will be reduced compared with that on grass – meaning the ball will roll further on concrete. The ball travels so far on ice because the coefficient of friction is extremely low, even though the latter means the ball may slide more than it rolls. Ice surface

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The Environment

High and mighty1

a Effect of altitude The altitude at which a golf drive is struck, relative to sea level, will have an effect on its distance. A drive struck at a high attitude will carry further through the air than a drive that is struck at sea level. This is because of reduced gravity and also because the air density is lower, which reduces the drag on the ball during its flight and increases the distance it travels through the air. The lower air density at higher altitudes also reduces the lift force arising from backspin, and at very extreme heights this may result in a shorter carry – for certain combinations of launch parameters.

Launch angle 14.3°, ball speed 240 km/h (149 mph) 240.5

Carry distance (m)

Launch angle 8°, ball speed 282 km/h (175 mph) 268.8 277.1 278.0 271.6 269.7

Shape of the Earth Distance from the centre of the Earth to the poles: 6357 km (3950 miles)

4369 m* 3048 m 1524 m 305 m 152 m Sea level

239.6 236.8 231.1 230.4 229.5

267.9

4369 m* 3048 m 1524 m 305 m 152 m Sea level

Carry distance (m)

Launch angle 11.5°, ball speed 269 km/h (167 mph) 275.1 273.3 264.2 252.3 250.4 248.6

4369 m* 3048 m 1524 m 305 m 152 m Sea level

Carry distance (m) Distance from the centre of the Earth to the equator: 6378 km (3963 miles)

o Effect of gravity The surface of the Earth is actually further away from the centre of the Earth at the equator than at the two poles. This has been caused by the planet’s rotation, which has resulted in forces changing its shape from a sphere to an oblate spheroid. This extra distance from the centre of the Earth to its surface reduces the effect of gravity on the ball – meaning the ball will fly further in the air at the equator.

Launch angle 12°, ball speed 237 km/h (147 mph) 216.6 218.4 216.6 213.0 212.0 211.1

4369 m* 3048 m 1524 m 305 m 152 m Sea level

Carry distance (m) * 4369 m (14,335 ft ): altitude of La Paz Golf Club, Peru, the highest golf course above sea level in the world.

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Golf coaches are often expected to dissect a golfer’s swing technique with the naked eye for a movement that is over within approximately 1.2 seconds. This is certainly a challenging task, even for a highly experienced coach. Therefore, the introduction of technology such as video cameras and performance analysis software has assisted the golf coach. The golf swing is one of the most difficult movements in sport, but recent advances in motion-capture technology, computer simulation models and pressure measurement devices have allowed researchers to analyse its unique mechanics and offer invaluable insights into what a great swing ‘looks like’. Making this wealth of data accessible to golfers and their coaches is the key to improving golfing performance. In this chapter, Robert Neal, a leader in the field of golf biomechanics, and Mark F. Smith apply their wealth of scientific knowledge to decipher the complexities of coaching technology.

chapter five

coaching with technology Robert Neal and Mark F. Smith

Can 3D motion analysis improve golf performance?

How can 3D swing analysis improve my golf?

There are many benefits for the golfer who chooses to have movements over time, improving the functioning body so that their swing analysed in three dimensions. Just think of the a more efficient and powerful golf swing can emerge. 3D analysis as a quantitative assessment of the swing. The ‘numbers’ can be compared with an age-and-sexTo properly analyse the swing in 3D, the golfer must use a comparable model and priorities for improvement can be system that is capable of measuring all six degrees of freedom readily determined. Tracking progress as the swing changes (DOF). This term is used by engineers to describe the six is a straightforward process using this type of technology. possible movement directions or axes in which a rigid body A further benefit of doing a 3D swing analysis is that physical can move in 3D space. A simple way of thinking about this limitations (such as stability, inter-segmental co-ordination and concept is to imagine the axes that the shoulder can move line weights _ but notflex sure mattersabduct as these are supposed represent display control, dynamic flexibility, strength, power and so on) can about: it can or itextend, or adduct (side totoside be highlighted. This information can be used to underpin the movements), as well as undergo long axis rotation. These prescription of exercises that are designed to change a golfer’s three axes of rotation would correspond to three DOF. In

o Candid camera

In the 1960s and 1970s the Photosonics camera became the workhorse in biomechanics, since its features were perfect for scientific study. You could ‘phase-lock’ multiple cameras, the film was pin-registered (this characteristic improved the accuracy and speed of digitizing later on) in the camera, lenses could be swapped easily, and you could achieve framing rates of 500 frames per second.

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o Computer power

In 1971, Abdel-Aziz and Karara1 published their seminal work on the reconstruction of 3D position in space from 2D co-ordinates of the same points on film, and by this time computing power was sufficiently advanced to implement the mathematics. By the early 1980s, 3D studies were becoming more common as computing power continued to improve and researchers were prepared to increase the complexity of the models that were used to analyse human movement. Neal and Wilson2 published the first paper on the 3D kinematics and kinetics of the golf swing.

Coaching with Technology

sort of technical drawing of dated cine camera that usually used b&w film (at high speed)

conjunction with these, the arm is also able to move sideways, thrust forwards or backwards and lift (up or down). These three translations represent the linear DOF.

amount of upper thorax (UT) or shoulder turn, in the golfer’s language, can be measured to less than ±0.5 degrees with some systems.

The motion-tracking system depicted (below, right) uses the principles of electromagnetic induction to determine the position and orientation of the sensors attached to the golfer’s body. The sampling rate for this type of hardware is 240 Hz, which means that the position and orientation of the body segments are gathered 240 times every second. Software is used to convert the sensor information to variables that are meaningful to the golfer and the golf coach. For example, the

Some 3D systems useoptional optical methods to determine the figure ..whate ‘standing area’ under position in 3D space of reflective markers (below, left). Most of these systems needline at least eight or more – often weights present grid 10 on ormonitor screen 12 – high-speed video‘wires’ cameras set up in a room in which from sensors pads 1pt the golfer hits shots. The golfer clothing, standwears areadark, line tight-fitting 05 pt and retro-reflective markers are placed on selected body points. These markers are tracked as they move in space and software is used to build an animation of the golfer as they hit shots.

o Video capture

o Super sensors

From the 1980s to today, multiple ‘video’ cameras have been used along with retro-reflective markers to track the movement of these points on the body. Here you can see the cameras and the markers attached to a golfer as they hit shots (in practice, more than four cameras are used). The trajectories of these markers are then used to create a 3D ‘avatar’. Sometimes other technologies are used (e.g. electromagnetic systems or rate gyroscopes, magnetometers and accelerometers) to investigate golf swing mechanics.

Sensors or markers, depending on the technology being used, are attached to the golfer’s body so that the movement (position, velocity, acceleration) of various body segments (e.g. hand, forearm, club, head and so on) can be measured. Key positional information such as the address posture or impact position is provided for the golfer and these data can be compared with a range of acceptable values (given the sex, age and experience of the golfer). Higher-order kinematic data provide insight into the speeds and accelerations experienced by different parts of the body during the swing.

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Do ball flight data help the average golfer?

What can I learn from watching my ball in flight?

Ball flight information is extremely valuable to the average golfer because the player can, through observation, deduce what the club was doing at impact. The trajectory of the ball, the sense of the impact location of the club head and the shape of the divot (when appropriate) taken together can give you most of the clues you need to determine, with a high degree of certainty, the way the club head moved to cause the ball to fly that way. First, the golfer must have an understanding of some basic principles of impact, spin and trajectory of a ball so they can take full advantage of any information they gather. Impact between the ball and club lasts for a tiny fraction of a second – less than 1/2000th of a second to be precise – yet during this time the club transfers all the necessary information to send the golf ball on its way. The impulse applied by the club, coupled with the forces of gravity and air resistance, determines the trajectory of the ball during flight. By applying the basic rules governing ball flight, a player can begin to deduce reasonably accurately what the motion of the club was at impact. For example, a player watching their ball fly in a straight trajectory (with no sideways curve), but to the left or right of the intended target, can conclude that the club face angle and the club path were aligned – or collinear – but not correctly oriented with respect to the target. Similarly, if the initial direction of the

a Slice

The red arrow represents the direction in which the club face was pointing at impact and the blue arrow is the club path. Because the path is more to the left (out-to-in) than the club face angle, the ball curves to the right (a slice for this golfer). An impact near the heel of the club will exacerbate the slice spin applied to the ball.

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Coaching with Technology

ball is towards the intended target, the player can conclude that the face orientation at impact was correct. Understanding ball flight also helps when hitting from the rough – the ball will not curve in a slice or hook as much. In other words, most golf shots fly pretty straight when hit from the rough. Lastly, short irons produce more backspin on the ball than a driver and, as a consequence, the ball will not curve as much in flight if the club path and face angle are not collinear.

Intended and actual ball flight

Ball flight

Target line

Ball loft

da Loft

Viewing the impact between the club head and ball side-on, the most important physical parameters to understand are the club delivery data (vc and α) along with the ball launch conditions (vb, β and ωb ). When there is a difference between the angle of attack (α) and the dynamic loft of the club ( θ), then spin (ωb ) – probably backspin – is created on the ball.

18 9

loft (m)

27

0 0 18 36 54 72 90

135

distance (m) Target

ωb

Vc Angle of attack

α

Vb Launch angle β

θ

Centre of mass

Sideways trajectory

18 36 54 72 90

distance (m)

135

Need to know θ = dynamic loft: The loft (angle) of the part of the club that makes impact with and influences initial direction of the ball, relative to vertical or horizontal (vertical /horizontal = zero degrees). α = angle of attack: The vertical (up-down) angle at which the club head is moving at impact. Positive means hitting up on the ball, while negative means hitting down on the ball. β = launch angle: The ball’s initial vertical angle relative to ground (horizon) level. ϕ = face angle: The angle of the part of the club that makes impact with and influences initial direct of the ball, relative to the target line (left–right). V = velocity: Vc represents the club head velocity into impact. Vb represents the ball’s initial velocity. = spin rate: b represents the angular velocity around the ball’s centre.

ω

Target

g Torque

ωb γ

ω

ϕ

Vb

Vc

γ = path angle of club to target line (TL)

Similarly, when viewing the collision of the club and ball from above, a torque will be applied to the ball that causes it to spin and eventually deviate sideways. Of the two factors, path angle of the club (γ) and face angle (ϕ), the face angle is much more important in determining the starting direction of the ball. For most impacts, including putting, face angle accounts for 85 per cent of the ball’s initial direction of movement and the club head path accounts for the remaining 15 per cent.

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How can golf apps improve swing dynamics?

Can I use my smartphone to improve my golf?

Over the last 20 years, video technology has grown in both popularity and sophistication. Increasingly being used by top coaches to study the swings of the best players in the world, video has helped coaches understand what good players do (and don’t do) and so has helped inform their teaching. The advent of good-quality cameras in smartphones and of golfswing software in the form of downloadable apps offers the golfer a compact video-capture-and-analysis package that could, if used appropriately, provide some benefit in helping to improve their game. But is there evidence that supports the effectiveness of these apps?

that for video footage to be useful the player must have sufficient knowledge of golf swing mechanics to undertake some basic analysis of their technique by themselves. In other words, the player must know what they are looking for and must be consistent in their approach to filming. It probably makes sense to have the objective eyes of a teaching professional do the analysis initially, but once the player understands what needs to be monitored, the smartphone video can prove to be extremely valuable.

An app for that Interestingly, there is mixed experimental evidence as to the real benefit of video analysis and feedback in improving motor performance for movements such as the golf swing. Certainly, findings taken from other sports, such as tennis1–2 and swimming,3 and from other motor skills such as surgery,4 seem to suggest that video feedback has no meaningful impact on skill acquisition (the ability to learn and then perform a task consistently and accurately) compared with traditional verbal or instructional feedback. On the other hand, research has also revealed that gymnasts5 and golfers6–7 have benefited from comparing video footage of themselves to footage of more skilled performers. Evidence also suggests that when coaches watch video footage they are more likely to empathize with their player’s thoughts and feelings, and therefore the use of this technique can facilitate a more supportive relationship between teacher and player.8 Taken together, there does appear to be some benefit of video capture in improving performance, but it is dependent on the extent of understanding and practical application a player possesses. For a player wishing to make best use of this easy-to-access technology there are some fundamentals that must be followed. Dr Robert Neal, a world-leading golf biomechanics specialist and authority on swing analysis, insists 122

Coaching with Technology

TL

o Get smartphone

FO

Research suggests that using video feedback to gather information about a player’s swing can improve the player’s effectiveness.7 When using a smartphone app for this purpose, it is important to ensure that the player is filmed both down the target line (TL) and face-on (FO). Also, if looking at the video without a coach, it must be clear to the player what they are looking for – for instance, head position or spine angle – and what they wish to improve. And they need to know how to apply the changes correctly.

Pocket coach

Highly skilled player at impact

Highly skilled player at address

go Phone for help Some of the key differences between the way highly skilled and low-skilled players swing the club and move their bodies can normally be picked up when using video capture technology from a smartphone. The images show a highly skilled player captured at different times during the swing – the red lines highlight face-on/target-line positioning as shown on the app.

Highly skilled player post-impact

d Key differences The application of decades’ worth of evidence, on-course observation and technological advancement has enabled detailed differences between skill levels to be quantified. The most common differences are summarized in the table below.

Variable

Highly skilled player

Low-skilled player

Pelvis sway

No sway away from the target on the backswing. Centre of pelvis moves approximately 10–13 cm (4–5 in) towards the target on the downswing.

Pelvis sways away from the target on the backswing (often of the order of 5–15 cm/ 2–6 in). It does not sway laterally towards the target on the downswing.

Club path/ swing direction

The trajectory of the centre of the club face on the downswing from the time that the shaft is parallel to the ground ‘matches’ the trajectory on the follow-through, as viewed from down the target line (neutral club path).

The trajectory of the centre of the club face on the downswing from the time that the shaft is parallel to the ground is ‘above’ the trajectory on the follow-through, as viewed from down the target line (out-to-in club path).

Spine angle

Maintained through the backswing, downswing and early follow-through. When viewed from down the line, the pelvis does not thrust towards the ball.

Spine angle changes as the pelvis thrusts forward, towards the ball. This phenomenon commonly occurs on the backswing and then increases on the downswing.

Head sway and lift

Head moves a few inches away from the target and usually drops a little on the backswing. On the downswing it drops a little further and moves laterally towards the target so that it is close to where it was at setup.

Head either sways excessively or remains too still as it lifts up on the backswing. On the downswing, it often rises more and is commonly closer to the target (in the sway direction) than it was at setup (‘in front of the ball’ in golf parlance).

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SCIENCE

IN ACTION

pacing the effort

It is easy to forget that golf is not just about hitting accurate shots consistently. A coach can also help with the physical and mental strategy involved in playing a whole round or, for top players, a tournament. Pacing is playing at a steady rate in order to avoid overexertion or underperformance. Literally meaning a rate of movement or progress, and traditionally used as a unit of measurement, ‘pace’ originated with the ancient Roman soldiers who marched in paces to ensure they kept their ranks with precision.1 This practice continued in most European infantry armies for centuries and, given the physical and mental importance of entering battle in an optimal physical condition, the regulation of pace during such marching would have been pivotal in ensuring overexertion was minimized and essential metabolic reserve preserved.2 Within the context of a round of golf, a golfer’s physical pacing must ensure they are able to maintain their effort around the course, staying fresh for each shot. More importantly, however, is a golfer’s use of mental energy. Seeing the course as 18 distinct sections ensures they have a planned strategy for each hole: having decided where to place the ball, making the shots they feel comfortable playing, knowing when to take a risk, finding ways to feel relaxed throughout the round and not dwelling on past shots. This conscious act of planning a set of actions designed to achieve the goal of a low score – the strategy – requires knowledge of the course so that a player can complete the round on a shot-by-shot basis without unnecessary physical effort and mental strain.3,4 Using a course planner to set out your strategy, knowing your distances, regularly referring back to these in anticipation of your next shot, and managing your physical and mental reserves will all help you to get to the 18th green in the same shape in which you left the first tee.

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Coaching with Technology

a Water works

South Korean Tour pro K. J. Choi takes on fluids during the PLAYERS Championship at TPC Sawgrass. Maintaining appropriate fluid and nutrition levels out on the course helps to ensure that a player stays in peak physical condition throughout a round. It has been proven that doing this also contributes to sustaining mental focus and alertness, essential to good decision-making during play, for individual shots and planning your whole round.

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How can movement quality during the swing be assessed?

What methods are available to help me analyse my swing?

In golf, there are three main technological methods for providing three-dimensional representations of golfers’ shots: optical systems, electromagnetic solutions and microelectricalmechanical systems (MEMS). Optical and electromagnetic systems are true 3D measurement technologies, while MEMS are ‘pseudo-3D’. True 3D systems are capable of measuring the full six degrees of freedom (6DOF) required for the description of movement of rigid bodies in 3D space. The pseudo-3D systems only measure three degrees of freedom, usually giving information on the orientations of body parts, but not their positions in space. The key benefit of the 6DOF systems is that these systems give the complete picture without the necessity of running other technologies. Optical systems track reflective markers on selected landmarks of the body by automatically distinguishing the markers on the video image from the background. The horizontal and vertical co-ordinates of the markers as ‘seen’ by multiple cameras are

used to compute their 3D trajectories. A calibration procedure is necessary prior to data capture to obtain internal camera parameters for completing the transformation from 2D to 3D. Additional software is used to compute the 3D rigid-body motion, using previously defined relationships among the markers. Electromagnetic systems rely on the strength of induced currents to determine the position and orientation of sensors attached to the golfer’s body relative to the source of varying magnetic fields. MEMS uses a combination of rate gyroscopes, accelerometers and magnetometers (which determine the angular position of the Earth’s magnetic field) to accurately measure the orientation of sensors attached to the player’s body. These systems can provide precise information on the rotational degrees of freedom but give no information on the position of the sensors in space. Systems based on these technologies require additional input for a coach or player to make comprehensive assessments of movement quality.

Movement sensors Rear

g Electromagnetic systems Front Head

Upper back Upper arm 1 Lower back/ lumbar Wrist Thigh

Upper arm 2

Hand

Ankle Foot

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Coaching with Technology

Today’s state-of-the-art electromagnetic systems offer a complete 16-body-segment model (using 12 sensors). Recent advances in the technology mean that the system can be almost wireless, with the sensors connected to a smartphone-sized device that clips to the belt and transmits the data via a radio link to the computer. Sensor currents are read and processed by the electronics unit before the data are sent to the computer. Complete signal processing and transmission occurs in less than 10 ms. The strengths of these systems are the wireless transmission of data, high sampling rate (from 120 Hz wireless to 240 Hz if tethered), simplicity of calibration, feasibility of attaching sensors to the club, possibility of full body-rendered 3D animation in real time, and that the systems are portable, quick to set up and can be used indoors or outdoors. Disadvantages are that movement must be within the calibrated space of the transmitter (a volume of approximately 2 m3 (71 cu ft) to ensure accuracy of measurement) and that large metal objects can interfere with data from the unit.

Big screen simulation

a Indoor setup

Wireless sensors are attached to the body segments and software is used to convert the electrical signals into orientation data. These data are transmitted via radio link to the computer for additional processing and conversion into graphic representation – in this case indoors, projected onto a screen in front of the golfer, offering real-time feedback.

On reflection

a Optical systems

These use reflective markers placed on the golfer to reconstruct 3D movement. Once the marker trajectories are known, software can create an animation of a rigid-body representation of the body and calculate various kinematic parameters. Key advantages of this system are that there are no cables, high sampling rates are possible (up to 500 Hz), calibration is anatomically referenced and full body-rendered 3D animation is possible. The disadvantages are that most systems must be used indoors, with subdued lighting, the calibration process is complicated and takes a long time, and no real-time visual feedback is available.

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equipment: the wedge

Who isn’t amazed at the skill of a Tour player who can hit the ball from 68.5 m (75 yards) off the green and spin it back 3 m (10 ft) to a tight pin position, or who can gently flop the ball over a trap with just a stride’s length of green to play with? The best players in the world are able to demonstrate such control and precision with their short game because, first and foremost, their swing technique is impeccable. However, a good player should also recognize that their weapon of choice can make a difference when it comes to being inch-perfect around the green. Prior to the 1930s, a single pitching wedge – commonly known as a ‘jigger’ – emerged to assist the golfer in recovering from tricky positions, such as the sand. With reduced loft to prevent digging into soft ground, the low launch angle had the unintended consequence of creating high resistance when attempting to dig the ball out from buried lies. In 1931, Gene Sarazen evolved the wedge design, thereby creating the ‘second wedge’, or sand wedge. For several decades following its initial invention, the standard pitching wedge maintained a

loft of 48–50 degrees while that of the sand wedge was slightly higher at 54–56 degrees. It wasn’t until the 1980s that proponents of the short game seriously began to rethink the wedge design with even greater loft. Innovators, with scientific minds, realized that the traditional wedge design wasn’t adequate to handle the increasing number of new courses featuring elevated and undulating greens. The development of higher-loft clubs with reduced bounce enabled access to a larger number of tight pin positions. While the driver, iron and putter have benefited from significant leaps in technological development, the wedge has lagged behind slightly, receiving the lowest amount of engineering ingenuity. It is unlikely that this has been missed off the major manufacturers’ to-do list, so it is more probable that the wedge is pretty much fit for purpose as it stands. However, scientifically informed innovation has brought some important changes to the wedge to help the player, including variations in head design for a lower centre of gravity, improved sole shape to reduce bounce and features to increase ball control and spin rate off the face.

Loft conversion Pitching wedge

44–48°

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Gap (approach) wedge

50–52°

Coaching with Technology

54–56°

Sand wedge

Lob wedge

58–60°

g Typical lofts

Modern wedges are available in just about every loft from 44–60 degrees. Although generally wedge lofts come in even numbers, each manufacturer has a different take on what the standard loft is for each of the four wedges.

Spin doctor Quality of impact Impacts below the centre will result in the golf ball being launched with more backspin while those above the centre will result in the golf ball being launched with less backspin.

Ball A softer covered three-piece ball results in creating a greater coefficient of friction. At an impact speed of 37 m/s (83 mph) the measured backspin of a three-piece ball has been recorded at 178 rps for an impact angle of 45° (e.g. pitching wedge). The corresponding value for a two-piece ball was 171 rps for the same impact angle.1

Dynamic loft

Club head path

Spin loft For a given club head speed, changing the relationship between the dynamic loft and attack angle in theory alters the spin loft and therefore the spin rate of the ball. Although moving the ball back in the stance generally creates a more negative attack angle, the dynamic loft will be offset by a similar amount, resulting in an unchanged spin loft and therefore unchanged spin rate.

Spin loft Horizontal = 0˚ Angle of attack

Club head speed Given that all other parameters remain the same, the faster the club head is moving through impact, the more spin will be generated.

Face surface At a loft of 50° (e.g. gap wedge) and an impact speed of a fraction over 46 m/s (around 100 mph), evidence shows that a rougher surface imparts approximately 250 revolutions per second (rps) of backspin to the golf ball compared with only 150 rps for a smoother surface.1

d Bounce The bounce of a club is defined as the angle, in degrees, between the ground and the club’s sole plane. At impact in soft turf or sand, a higher bounce angle increases the upward resisting force on the sole of the club to prevent excess digging. For firm turf or sand, lower bounce angles improve contact by reducing this resisting force, allowing the leading edge to easily slide underneath the ball.

o Spin The amount of spin imparted to the golf ball by the wedge is affected by a number of factors – the face surface of the wedge, the path of the club head as it approaches the ball, the loft of the wedge, the speed of the club head at impact, the specific quality of impact and the ball itself.

Club bounce

High bounce

Bounce angle Promotes small, shallow divot

Standard bounce Medium divot

Low bounce

Tends to dig more in soft conditions

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What are the advantages of coaching technologies to the coach?

Can a coach with the latest technological tools improve my golf? On track

Going back not that many years, golf coaches had to rely only on their own sensory inputs – watching and listening to a golfer – and then filtered the necessary information from the unnecessary. Today’s golf coaches have access to a multitude of different technologies which can provide information to guide their coaching decisions. So are today’s coaches any better because of the technological devices now available to them? It can be argued that having lots of different types of data from various technologies does not make you a good coach. In fact, bombarding a player with unimportant information might be detrimental to helping them learn how to improve their golf. The golf coach must sift through the available information for the most important feedback. It is true, however, that putting high-tech devices in the hands of a good coach will allow them to make more rapid progress with a player. Furthermore, the feedback from high-tech devices, if provided in a systematic way, can help the golfer to understand their swing better and gain a feel for a correct pattern of movement more rapidly than they would be able to without access to such data. There are many new tools which help a player and their coach to focus on improving technique. Very high-speed cameras and ‘launch monitors’ now enable the recording of the impact of the club and ball – an event which takes just 450 ms. Tracking systems are being used to understand the movement of a ball after impact. Using radar, the trajectory, speed and even level of spin of a ball can be mapped, providing a player with detailed feedback on the outcome of their swing. Putting technique can also benefit from tracking systems – they allow the coach to measure the motion of the putter during the stroke, particularly as it approaches the ball. The coach can monitor the angle of the putter head at impact to determine if the player is ‘cutting’, ‘hooking’ or squarely hitting the ball. Obviously, armed with such knowledge, the good coach can help the player make corrections to technique in order to improve the quality of impact. 130

Coaching with Technology

g Tracking devices According to ball flight laws, the club path and face angle are key parameters in determining the trajectory of a shot, and it is possible to analyse them using modern imaging equipment. The latest devices enable a golfer to monitor the swing, club face angle and ball launch to the ball’s trajectory, all in real time.

Putting technique

g Sonar

When evaluating putting technique, it is impossible for the golfer or coach to know the face angle and path of the putter when the putter makes contact with the ball. Sonar or electromagnetic tracking systems allow the coach to measure the motion of the putter during the stroke and as it approaches the ball.

Swing forces

g Force plate

The force plate differs from the pressure mat in that it typically measures the three components of the ground reaction force, or GRF (medio-lateral, antero-posterior and vertical), the centre of pressure and the free torque applied to the ground. This helps the golfer to understand weight transfer and shear forces during the swing.

High-tech feedback Less than 15 years ago, most golfers just bought clubs off the shelf and there were very few choices in shafts and head designs, for instance. With new technology the coach can ensure that the clubs a player selects match their technique and physique.

Computers provide the golfer and their coach with immediate feedback on all aspects of the golfer’s swing, with cameras and sensors capturing movement in detail.

This shows a Golf BioDynamics motion -capture system used in conjunction with a pressure mat. This enables a golfer and coach to analyse the swing and make improvements to technique in real time.

A coach who does not use high-speed cameras or launch monitors can only guess at what happens at impact.

Research laboratories have long had access to sophisticated devices for measuring the ground reaction force (GRF) applied to the golfer. Only recently, however, have portable and less expensive systems such as pressure mats and force plates become available for the golf coach.

o Coaching aids There is now a whole range of relatively inexpensive devices available to assist a golfer and their coach in analysing many aspects of the swing, including high-speed cameras, sensor-equipped clothing, pressure-sensitive pads and radar systems. However, interpreting the most useful data to improve the golfer’s game is still down to the skills and knowledge of a good coach. 131

What is the future of golf coaching technology?

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Pelvis is further from target at impact than at address

Pelvis sways away from target

+8

–12

0

Impact

Address

0

0.4

O.8

1.2

Time (s)

Pelvis sways towards target on backswing

Top of backswing

Weight moves onto lead foot, pelvis is closer to target at impact than at address

Pelvis does not sway from target +8

0

0

Impact

–12

Address

From a scientific perspective, biofeedback is the process of gaining greater awareness of the many psychophysiological systems through the accompanying responses that occur during movement. Primarily using instruments that provide information on the activity of those systems, the objective is to increase voluntary control over physiological processes that are otherwise outside awareness, using information about them in the form of an external signal. Some of the processes that can be monitored during golf include brainwaves, muscle tone, skin conductance, heart rate, pressure patterns and pain perception.1–7 Taken together, biofeedback may be used to improve performance and control the physiological changes which often occur in conjunction with changes to thoughts, emotions and behaviour. Eventually, the golfer may be able to maintain such changes without the use of extra equipment, so that they become automatic.

Pelvis movement

Hip sway (cm)

So what does the future hold for golf coaching technology? And how may recent scientific discoveries begin to shape the way the golfer trains and competes? The possibility of a fully integrated system of sensors and feedback devices, positioned over the body of the player, which allows both coach and golfer to access real-time biofeedback in the field, is not far-fetched. Biofeedback, in a practical context, is defined as a training programme in which the golfer is given information about movement (for instance, position or orientation of a body segment, speed of movement and co-ordination) which is not normally available, with the goal of improving swing kinematics. The feedback can be auditory or visual, the benefit of auditory real-time feedback being that the golfer can monitor the feedback and still watch the golf ball. The most important and underlying objective of any form of biofeedback provided to the golfer is that they can gain the correct feel (in their body) of the desired movement, without any external forces being applied by an instructor. In golf coach-speak, the player can quickly learn to ‘own’ the new movement pattern.

Hip sway (cm)

Can biofeedback advance golf performance?

0.4

O.8

1.2

Time (s)

Top of backswing

o Audio aid Auditory biofeedback can be used to change a golfer’s movement pattern. At halfway through the downswing (top) the pelvis has rotated too much and not translated sufficiently towards the target. The golfer would know this immediately because no beep would be heard. Below, the golfer would have heard the beep, letting him know that his hips have moved far enough towards the target – into the indicated zone – and that he can begin rotating his hips as rapidly as possible. Equally, if he had moved his hips too far to his left the beep would also have gone off, which is a disadvantage of the system.

Head movement

g Head down The golfer initially lifted

Continuous beep

A

his head up too much on the backswing in A. By using a ‘virtual ceiling’ placed over his head, the player can learn to change his movement. Starting his backswing with the audio tone on, the player has to keep it on during the entire backswing in B. He quickly learns what it feels like to maintain the correct positions, including spine angle.

B

Future training aids

g Biofeedback future

The visor acts as a multi-system device, monitoring, recording and then feeding back the most vital data to the golfer.

Micro-sensors and gyroscopic devices detect body position, muscle activation patterns, breathing response, heart rate and skin temperature.

So what may the future of golf biofeedback technology hold? Although yet to be fully realized, emerging research is leading to the evolution of complete biofeedback systems that assist in the optimization of golf performance.1–7

An ‘intelligent training pod’, worn on the belt, collates data measured by on-body wireless devices. Feedback in the form of coaching advice, vibrations or sounds can be delivered through the visor. Sensors within the club head and shaft provide instant feedback on swing speed and impact position.

Each smart shoe uses ground contact sensors to measure pressure and force information throughout the swing.

A fully responsive online software package collates all golfer data to build up an individual training programme based on the player’s strengths and weaknesses.

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To become a better golfer requires time, effort and, of course, plenty of patience. With it taking roughly 10,000 hours of purposeful practice to hit the lofty heights of real golfing success, the search for ways in which practice can become more effective, time-efficient and individualized has led to science for the answers. A good golf practice strategy should be open to change and be continuously adjusted as skills, time and equipment vary. As the player’s game changes, so will strengths and weaknesses. Practising the golf game properly is vital to improving. Knowing how to practise increases self-confidence, reduces scores and lowers golf handicaps. It also increases the fun of playing as scores drop on each round. John Hellström and Mark F. Smith consider how science has aided our effective implementation of practice regimes to further golf performance.

chapter six

the practice process John Hellström and Mark F. Smith

Does ‘deliberate practice’ improve golf scores?

Can I improve my golf just by playing more often?

When watching the world’s best players compete for top places at the Majors, the extensive training each has undertaken doesn’t necessarily spring to mind. Such expertise develops over an extended period of time.1 A training period of 10 years or some 10,000 hours may be needed to become an expert, as first suggested by studies on chess players and musicians.2,3 Similar amounts of training are also needed to reach an international level in some sports.4 Neurophysiological evidence indicates that the brain slowly transforms as a consequence of practice.5 Each time a pattern of activity is repeated, new connections between brain cells, called synapses, are created, reinforcing neural pathways and enhancing the player’s ability to perform that activity automatically.

Given that the average golf handicap index is 16.1 for men and 28.9 for women, according to the United States Golf Association, many are far away from being competitive at high level. Most players have stopped lowering their average scores well before they could shoot under par regularly. Research has started to indicate that piling in the hours on the course or practice green alone may not be enough to improve. Even at a young age, playing for fun and playing to win need to be carefully managed to maximize the golfer’s chance of long-term success – having fun is important for the juniors beginning a new sport in order to maximize participation and minimize dropout.6,7 Early specialization may not be needed in golf, where top performers often are in their mid-30s.5

Growth of a player As a beginner starts to play golf, opportunities to engage in unstructured free play and practice often take up the large majority of available golf time. This is termed the sampling phase and is not governed by detailed score monitoring, performance analysis, or too much critical review of performance – in essence, the main goal is having fun.9–11 The gratification is immediate and there is no focus on correction. If a player wishes to advance and commit, the number of activities decreases and the type of practice begins to change. The volume of play typically decreases and deliberate practice increases. This means that golf gradually becomes the top priority, with clear goals, carefully monitored training, and focus on feedback and immediate correction (known as the investment phase).

100 90 80 70 % of time spent

a Structured learning

60 50 40 30 20 10

Play Deliberate practice

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0

Sampling phase (6–12 years)

Specialization phase (13–15 years)

Investment phase (16+ years)

What is clear is that those golfers who avoid becoming stale and unimaginative in playing and practising are able to continually improve by constantly challenging themselves. They set relevant goals, often with the assistance of a dedicated and supportive coach, and create training situations in order to help them exceed their current skills, encourage high focus during training, and enable evaluation of their performance.8 This is called deliberate training,3 and players need a high volume of this as they approach adulthood if they are to reach an international level in golf. Choosing the right training system, having the support, the right mindset and plenty of time to practise are the most effective ways to lower that handicap.

d Warm-up

A critical challenge for all golfers wishing to improve is to avoid ‘arrested development’. The concept, coined by Anders Ericsson, the father of ‘deliberate practice’, refers to a period of player development associated with automaticity and staleness instead of continued learning and improvement. Actively seeking out demanding on- and off-course challenges during practice increases the performance level and lowers scores.

Golfers who become world-class players continue to improve Amateur players who stop improving (arrested development)

Performance (average strokes to par on a course with par 72 and course rating 72)

Deliberate practice makes perfect

Peak of career

–5 0

18

36

0

10,000 20,000 Training time (h)

30,000

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What are the psychophysiological effects of a warm-up routine?

How does a warm-up before practice help?

Successful performance is built around routine – every great golfer has one. From the pre-shot ritual to the post-game analysis, building in repetitive patterns of positive behaviour aids a golfer’s preparation, on-course performance and postmatch reflection. A common routine within the professional golfer’s armoury is the essential, but often misunderstood, warm-up. Although not often shown in TV coverage, it’s easy to spend many hours at tournaments observing the top players on the practice ground. They work through the array of shots, calibrating their body and mind, and deciding final swing thoughts with their coach. This important ‘before-play’ aspect works on a number of mental and physical levels and all players can benefit.

As is often mentioned in popular coaching books and player manuals, one purpose of a warm-up is to improve the dynamic function of muscles by elevating localized blood flow, increasing temperature and activating key enzymes. Collectively, these processes get the muscles in a state of ‘readiness’. There is also evidence to suggest that undertaking regular golfspecific stretching before play can reduce the incidence of muscle strains.1,2 Research indicates that a warm-up employing dynamic stretching – an active movement that pulls the muscle into an extended position without exceeding its ability – results in greater club head and ball speeds than if the stretches are

Percentage levels of warm-up exercise by golfers preceding practice

Percentage levels of warm-up exercise by golfers preceding play

Never 61% Seldom 36%

Never 22%

Always 4% Always 10% Sometimes 19%

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The Practice Process

Often 13%

Often 4% Seldom 26%

Sometimes 5%

Benefits of a warm-up

done without movement or not at all. Additionally, this research found that players who undertook regular, golfspecific dynamic stretching before play achieved a higher number of centralized impacts on the club face than the static stretch group.9 Taken together, this equates to greater distance and more consistency. Devoting a little time before each round to a brief routine can also have a beneficial effect on the way the mind prepares for play. Studies of highly skilled tennis players have indicated that a warm-up consisting of practice swings can optimize arousal level and activate a player’s ability to engage in positive mental imagery.4 Given that mental imagery can be an effective way of reducing performance-related anxiety, increasing concentration and focus, and removing unwanted thoughts, the warm-up process may serve as a way to calibrate the mind as well as prepare the body.

All in the mind? 1 Research indicates that a warm-up routine of practice swings and light exercises puts the golfer’s mind in the right place and can lead to better performance.

Or more in the muscle? 1 A general body warm-up can increase muscle blood flow and body temperature, which speeds up contraction of the important fast fibres activated during the golf swing.7

2 Increases in blood flow to the brain enhance the nervous system, activating alertness and cognitive function.4

2 Static and dynamic stretching has been shown to alter the biomechanical length–tension relationship of shortened, tight muscles.8

3 Additionally, rehearsal of the desired swing movements at an optimal velocity may act to facilitate co-ordinated motor pathways and improve tempo and rhythm.5

3 Dynamic stretching has been shown to increase flexibility of the muscle– tendon units, helping the golfer to obtain the desired biomechanical dynamics throughout the swing.10

g Practice makes perfect

Whether preceding practice or play, evidence from studies on amateur golfers with an average skill level reveals that the likelihood of a golfer performing a warm-up routine is generally low.3, 6 Given the advantages to both mind and muscle, even the briefest activity – built regularly into a player’s time at the course – could have significant benefits for their performance.9

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How does a golfer learn a new swing?

How soon can I play without thinking about my swing?

Golfers who are starting their playing journey are often in awe of how easy it looks when skilled players swing. But how do they get to such a stage of performance? Cognitive psychologists have pondered such questions for over a century and have suggested a number of theories. One, which has gained popular support within sport science over the last 50 years, is that proposed by the renowned Fitts and Posner – a phasic conceptualization of motor skill learning evolves in the learner through three stages: the cognitive phase (understanding the swing); the associative phase (refining the swing); and the autonomous phase (making the swing automatic).1

In the early stages, there are typically many errors in the movement, with swing characteristics and ball flight being highly variable. The player searches for answers based on the basic fundamentals of the game and movement.1 Learning the golf swing demands a lot of attention and concentration, and players do not generally know what to correct in order to improve. They therefore need specific instruction, demonstrations and other verbal information that will support their development. Research has indicated that those who learn to play golf at an early age may learn more implicitly than those learning at later ages.2 Young juniors may rely on

Process of deliberate practice

a Flow of learning

Coaches and players all face the flow of learning whenever they come to develop a golf swing. Practice, whether coached, instructed or self-initiated, leads players through a number of continuous periods of learning to true behaviour change.4 The extent of change, however, depends on a number of interconnected factors such as an individual player’s training history, biological age, instructional quality and the nature of practice.

Emotional centres

Cerebellum (posterior lobe)

Premotor area

Cerebellum (anterior cerebellum)

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The Practice Process

g Brain training

Deliberate golf practice induces changes in the grey matter of the brain,5 with changes being dependent on the learning stage the player is moving through.6 The posterior lobe of the cerebellum and emotional centres have a higher involvement during the early stage of motor skill learning,7 which may reflect the evolution of a rhythm for the movement sequence and conscious ‘emotional’ thought.8 When the rhythm has formed and become autonomous, the anterior cerebellum and premotor area become more active.

Learning progression

Stage one Unconscious incompetence This is where any learner starts – not being aware of the skills and behaviours that are needed. Golfers (especially beginners) often do not realize what movements are required to perform an effective golf swing. They do not know about posture, grip, arm positions or body rotation. Hence they have no mental representation of a movement, and so they are also incompetent at performing the movement.

Stage two Conscious incompetence An awakening has to occur to move to conscious awareness of the behaviour or skill. The player has to realize, from some source, what the swing entails. Coaches, peers and even watching the pros on TV can create this mental shift, bringing the skill into focus for the player, who then moves from unconscious to conscious by recognizing what movements are needed. When they try to execute the skill, they soon realize they are not competent. Once this realization is internalized the player is ready to practise towards personal change and development.

sensorimotor processing (knowing how a correct movement feels and what it looks like) to a greater extent than adults who rely more on declarative (or explicit) memory (understanding the logic behind the movement). This may have the effect that juniors build stronger, longer-lasting motor patterns. As deliberate practice continues, the variability of performance from swing to swing decreases, with the golfer being able to predict outcomes for different tactics, until eventually they master the swing movement.3 The player better considers the

Stage three Conscious competence To get to this step, deliberate practice must take place. In this period the learner can now execute the swing with fluidity and consistency. In essence, they know how to do it and can do it. The behaviour or skill does not yet happen naturally. The player must think of it, and be conscious of doing it, for the behaviour to occur. But they can now do it competently.

Stage four Unconscious competence To get to this phase, where the behaviour comes naturally without thought, requires the golfer to keep on working, deliberately practising using the skill. Eventually, the skill is used without a thought. That’s the start of unconscious competence. At the end the player is proficient without thinking.

lie of the ball, target, swing and club selection, and continues to refine their game in the second phase. The motor energy cost is lower – that is, they can hit the ball progressively further with less effort. The golf swing becomes more or less automatic in the last phase.1 The player does not have to attend to the details and is able to perform the swing without thinking about it. Players in this third phase are able to detect their own errors and make proper adjustments to correct them. The variability of performance becomes much smaller, and the performance improvements become gradually slower. 141

SCIENCE

IN ACTION

expect the unexpected

However much you practise, there will always be shots that do not turn out as anticipated, even if you hit the ball well. Hit exactly the same shot more than once and the outcome will differ each time. Therefore, the golfer must learn to expect the unexpected, and maintain a positive approach to their game. Research has shown that the most successful Tour golfers are generally more mentally astute, using more consistent pre-shot routines, planning more effectively when on course and being able to maintain high levels of confidence throughout their round.1 Golfers constantly measure their own performance, so it can be easy for them to lose confidence in their ability in unexpected situations. Previously, we have seen how maintaining a good mental attitude throughout a whole round is important to staying focused. Concentration, anxiety confidence and motivation are all key factors in effective golfing performance. If a golfer has developed a coping strategy to control these variables and bring about favourable outcomes, then that golfer will be better able to perform when unexpected events occur. One such effective strategy is the use of mental imagery. Before each shot, Jack Nicklaus would imagine playing the shot – where he wanted the ball to land, and how it was going to get there. Even in the most awkward of positions, imagining how the swing will feel and how the shot will look can help. Specific areas of the brain are activated when we make a movement such as hitting a ball, and evidence suggests that when we imagine making the same movement very similar areas of our brain are also stimulated.2 Mentally rehearsing the swing and how it will feel, and visualizing the outcome, can help maintain focus, motivation and confidence, and foster a balanced mental approach. Staying patient, accepting the bad with the good, and being prepared for the unexpected will help you to develop a positive attitude to your game.

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a Trunk call Everyone who plays golf knows that even a great shot can end up somewhere unexpected, such as next to a tree trunk, thanks to a gust of wind or an unwelcome bounce on the fairway. Learning to deal with the unexpected is an important part of playing golf well at all levels. Maintaining a positive attitude, staying focused on your next shot, and not dwelling on past shots, will all help you make the right shot decisions.

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What is the difference between learning and performance?

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Negatively accelerated Performance improvement

Linear

Time

Time

Positively accelerated

Ogive, or S-shaped Performance improvement

Given that a performance improvement ‘slow-down’ often occurs in golf, a number of plausible explanations can be deduced. The first relates to a self-identified performance proficiency – the level of playing ability a golfer is content with achieving. This typically relates to enjoyment and ability to complete the course in a reasonable number of shots. Another explanation, which is probably the more important to game improvers, is that the rate of improvement seems related to what is ‘left to improve’. In simple terms, this means that early on in the golfer’s development there is much room for advancement in skills. As the player reaches a certain level or standard, there is less room to improve and any remaining improvement may then be flatter – requiring more purposeful, refined and committed practice. This perceived slow-down in the learning process is termed the ‘power law of practice’.

Performance improvement trends

Performance improvement

An ability to predict both the quantity and quality of golf practice necessary to continually improve is critical to success. Why? Because without this aptitude learning would cease and performance not progress. Performance is the behavioural act of executing a skill at a specific time in a specific situation, such as swinging a club during a golf competition. This is often visible and measurable directly. Learning, on the other hand, is a change in the capability to perform a skill. It occurs as a result of experience or practice. It cannot be observed directly, as the processes leading to change of performance are internal, with different elements of the technique learnt at different rates.1 Investigations examining people learning refined motor skills,2,3 similar to those used in golf, have shown that the rate of performance improvement is usually higher at the beginning and lower later on. This decrease in improvement is called a negatively accelerated function of practice, and is probably the most common feature in learning motor skills.4

Performance improvement

What is the ‘power law of practice’?

Time

Time

o Learning curves In general, there are four different trends to performance improvement over a period of time: in a linear way (improving proportionally over time); negatively accelerated (improving the most in the beginning, i.e. the ‘law of practice’);5 positively accelerated (improving more in the end); and S-shaped or ogive (improving most in the middle). Negative acceleration in learning is affected by the time required to advance skills. A shorter time may result in a more linear progression, and a longer time in a curvilinear shape. It is important to recognize that these curves are hypothetically smoothed, with individual curves in real life likely to look more erratic. Players may experience any or all of these with different skills at any time.

Accurate and precise

Accuracy and precision

Inaccurate but precise

Accurate but imprecise

Inaccurate and imprecise

Reference value Accuracy Determining training goals helps to shape the quantity and quality of golf practice. Accuracy is measured as a central value (i.e. mean or median). For example, this may be the mean (average) distance of the group of balls to the target. On the other hand, precision (or consistency) is a measure of spread. This may be the distance between the shortest and the longest shot, or a distance measured as a standard deviation (i.e. a measure of variability around the mean). By using these measures to investigate the effects of training – for example, on impact location on the club face, where the ball ends in relation to a target, or even golf scores – practice can become more purposeful.

Frequency

a Practice with purpose

Value

Precision

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What forms of feedback improve golfer performance the most?

Should I listen to myself or to my coach?

Feedback is critical if a player wishes to improve their golf performance. Generally there are two types of feedback – taskintrinsic and augmented (or task-extrinsic). With task-intrinsic feedback, the golfer receives information from their senses. They can see, hear and feel the movement and the outcome. This concept of feel can be divided into internal (proprioception) and tactile senses. Skilled golfers can, for example, feel the pressure from the golf club at the shaft end, and then interpret the dynamics of the shaft and adapt the swing accordingly to obtain the desired impact.1 With augmented feedback, the player receives information from an external source such as a coach or a video camera. This provides information on which they may not have focused using their sensory system alone. So when should a player choose augmented feedback? The decision is often based on their experience level and which aspects of their game they wish to improve. Receiving external feedback may aid the learning process and motivate the player,

A small draw against the wind, while maintaining his balance … Nice! I’ll ask him what he thinks about the swing before giving my feedback.

allowing them to continue training towards a specific goal. It can be provided during the swing (concurrent) or after it (terminal). There are two sources of such feedback, known as knowledge of performance (KP) and knowledge of results (KR). Knowledge of performance describes how the body performs and the club is swung. Knowledge of results relates to the outcome, such as how the ball flies, how close it comes to the target and what score is achieved. However, feedback may also hinder learning if provided incorrectly or in an untimely manner. If the coach provides too much feedback too often, the golfer may come to depend on this information and play poorly when such feedback is not available.2, 3

d In the feedback loop Experienced players, through years of practice, are able to evaluate their swing themselves. They use their knowledge of performance to evaluate their movements and make corrections to improve efficiency, accuracy and consistency. A coach must be careful how and when they provide their augmented feedback to the player, motivating them and enabling them to become an independent self-analyser.

Nice impact sound. That felt like a well-timed swing … and I kept my balance! Yeah… Ball is drawing nicely against the wind… I like it!

What the player hears during impact provides information on the quality of strike.

A coach should adapt feedback to suit the player.4 A less skilled player will need feedback more frequently (every second or third swing) and in smaller units. As the player improves and the task is easier, the feedback can be less frequent (every seventh to tenth swing) and be more brief.5

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Visual appraisal of the shot outcome by the player, such as the ball trajectory, alignment and the club’s position on impact provide valuable feedback on swing effectiveness. How the swing felt, through the body’s internal proprioceptive feedback system, enables the golfer to make fine adjustments during the shot and helps with understanding the shot’s outcome. The sense of connection with the ground through the feet, and with the golf club through the hands, provides tactile feedback about the extent of pressure, strain and balance throughout the strike.

Decision-making

Lack of awareness of how the shot should feel Not ‘tuned’ to how a good shot should sound

Sees bank of trees

Sees bunker

Brain focuses on making the shot, and on the details of the swing and body position

Sees location of flag

Aware of flag position but not aware of wind direction

o High-handicap player When aiming for the green, the high-handicap golfer mainly focuses on seeing the hole’s position, and on surrounding landmarks such as the trees at the back, and the bunker, but overall their perception of the hole is not very detailed. Their brain focuses on hitting the ball the required distance to land on the green, and because of their lack of experience and skill, this level of golfer is less attuned to how a good shot should feel. Knows how the planned shot should feel through the swing and at impact High level of awareness of how a shot should sound

Not aware of contours of the green, and how the ball will roll on landing

d Low-handicap player An expert player uses their senses efficiently. They know almost instinctively how the shot should look, sound and feel, freeing their brain to focus less on playing the shot and more on the details of the most relevant environmental cues – such as subtle changes in wind speed, green contours and sandtrap positions – all leading to more accurate decision-making about the length and direction of the shot.6 Sees position of individual trees closest to green, and factors this into decision on where to aim the ball

Brain focuses on making decisions about the type, line and strength of shot

Sees bunker but is confident shot will fall short

Sees and absorbs details of hole, such as distance to green, positions of trees, movement of trees and flag in the wind.

Sees the location of the hole, but also the wind strength and direction from the flag, and factors these into where and how hard to hit the ball

Aware of the contours, and how the ball will roll on landing, and so decides where to aim the ball

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These are not grouped.. they are oversize re width..earlier iterations bled off page...

equipment: the driver

One of the most remarkable achievements in club design is the evolution of the driver. In golf, progress usually takes decades, but in the case of the driver, this can be measured in mere years. Club designers have continually pushed the boundaries of innovation, developing the size, shape and construction of the club head to maximize driver performance. The most influential changes in driver design appeared in the mid-1990s with the use of titanium, well known for its higher strength and lighter weight than steel. Designers began creating much larger club heads, while still meeting the weight specifications of a normal driver. This in turn had the effect of creating a higher moment of inertia and subsequently making it easier to hit the ball straight even for off-centre strikes. In a short space of time, club head volumes developed from 190 cc to 300 cc. The year 2000 saw the first 350 cc driver, followed in 2001 by a 400 cc driver and a 500 cc driver in 2002. At this point, the rulemakers began to propose limits on drivers as they were potentially seeing technology threaten to diminish skill level. So in

October 2003, the ruling authorities imposed a 460 cc limit on club head size from the start of the 2004 season. With restrictions of head volume introduced, club designers shifted their focus to explore shape, weighting and material properties. Recently, attention has turned to predicting club head drag forces and identifying specific geometric features contributing to the total drag (pressure and friction drag) on drivers. With club head speeds exceeding 161 km/h (100 mph) prior to contact with the golf ball, the driver is a bulky, intrusive object which can generate significant drag force during the swing motion. The shape of the club has a definite influence on this force, and golf club designers must account for this while trying to optimize the club shape. Manufacturers’ research has shown that the reduction in club head speed measured during player tests correlates strongly with the resulting increase in aerodynamic drag for extreme dimension club heads (i.e. 460 cc). The use of computational fluid dynamics (CFD) has enabled engineers to make small modifications to both the face area and the transition area from the face to the body of the club to help keep air flow attached to the head surface and reduce aerodynamic drag.

Driving design

a Modelling air flow

Engineers are able to model club head designs by applying computational fluid dynamic (CFD) technology. These techniques, often used in the aviation and automotive industries, provide cutting-edge modelling to replicate air flow dynamics around the head. The aim is to ensure the air flow does not separate during the early stages of the swing, resulting in lower drag in all orientations, and thereby improving the overall design and club head speed. Drivers now have increased dimensions and high inertia with low aerodynamic drag forces, enabling increased club head speeds and greater drive distance for golfers.

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The Practice Process

Low aerodynamic drag on club head

Shape influences the nature and size of wake region behind club

The shape of the head influences the attachment of air flow over its surface

By the rule

g Club head dimensions

The length of the club head shall not be greater than 12.70 cm (5.0 in) when measured from the heel to the toe.

Rules governing club head dimensions were introduced in 2004 because of the trend towards increased driver head sizes. The Equipment Standards Committee of the Royal and Ancient determined that driver heads larger than those already permitted were not traditional and customary. Many club heads have markings on the head to indicate approximate volume.

The volume of the club head shall not be greater than 460 cc. A maximum test tolerance of 10 cc is permitted.

The height of the club head shall not be greater than 7.11 cm (2.8 in) when measured from the sole of the club head to the crown.

Driving further

g Drive distances

Better equipment, along with the improved fitness of players, has meant that the average driving distance of PGA Tour players has increased by roughly one metre each season in the last three decades. This chart shows the trend since 1980. Early in this trend, testing showed that the average PGA Tour distance off the tee increased as the club head size increased.

218.5

1980 No data available

246.6 231.3

217.8

1985 No data available

254.2 237.7

223.1

1990 No data available

252.0 236.7 225.9

1995

236.7

289 283.5

229.5

2000

Lowest (shortest) average for a single player (m)

245.7

270.9 274.5

233.1

2005

260.1 239.4

2010

263.3 241.2

2012

263.3

Highest (longest) average for a single player (m) Average distance for a single player (m) Longest drive for a single player (m)

287.1 397.8 284.4 381.6 282.6 405.0

149

How important is effective green reading to putting performance?

How should I spend my time on the practice green?

Accomplished golf performance depends on abilities in the long game, short game and putting. Over 40 per cent of strokes are taken with the putter, so time spent practising with it should pay dividends when on course. Instructional literature on effective putting practice is often perceived as anecdotal and based on observations by top coaches and players, rather than on published scientific research. Recently however, scientists have begun to unravel the major factors that contribute to putting success, which, when deconstructed, may offer a solution as to how best to spend the time on the putting green. Experimental research has revealed that skilled golfers have in general a five-times larger deviation in distance (6.5 per cent) than in direction (1.3 per cent) when making those important long putts to the cup.1 Quite simply put, golfers tend to make more errors in how hard they hit the putt than in the line they start it at. However, mathematical calculations2 reveal that, as long as the ball is headed for the centre of the cup, it will go in even when a remarkably large distance, or range, error has been made. It will either just trickle in for a short (slow) ball or hit the back of the cup and bounce in for a long (fast) ball. The initial angular deviation from the perfect track must not be so large that the ball misses to the left or right of the hole (see captions right). Evidence has shown that, when skilled golfers were asked to make a series of 6 m (20 ft) putts across an undulating green, the ability to effectively read the green played a more substantial role in the overall success (that is, reducing the final distance of the ball from the hole) than technique or uncontrollable green inconsistencies. With further evidence highlighting the importance of green-reading ability in the reduction of direction variability in putting, it seems logical to suggest that practice scheduling should include sufficient time to develop the skill of reading a green.3–5 Green reading is a cognitive process, by which the player has to decide how hard 150

The Practice Process

Reading the green

Technical execution Green-reading ability

Environmental effects of green

o Reasons for shot accuracy Where the ball ends up after the stroke may have more to do with a player’s ability to accurately read a green than with the putting technique itself. Findings from a research study highlight that where the ball stops in relation to the target is more the consequence of green-reading ability (60 per cent), than of technical execution (34 per cent) or environmental effects of the green (6 per cent).1,4

to hit the ball and in which direction to hit it. Environmental forces, such as gravity, wind and friction (grass length and direction), affect the ball distance and direction. The ability to predict these forces, and the required club face alignment and club head speed at impact, is probably the most critical factor in putting success among skilled golfers.1 Many missed putts are wrongly attributed to poor technical proficiency, when it is more likely to be poor green reading that is the main cause of error. Thus, it is important to train with drills that give the player accurate feedback about the green conditions when hitting a putt, focusing on the most important part of putting.

On target 4.0 (13.12)

g Target range for a 2 m (6.5 ft) putt

Target range, m (ft)

3.5 (11.48) 3.0 (9.84) 2.5 (8.20) 2.0 (6.56) 1.5 (4.92)

–2 –1 0 +1 +2 Angular deviation from perfect track (degrees)

g Target range for a 3 m (10 ft) putt

5.0 (16.40)

As the distance between the ball and hole increases, the angular deviation from the perfect track becomes more important. Again, for a slightly uphill putt, for the ball to drop into the cup the target range can be anywhere between 3 and 5 m (10 and 16.4 ft). However, with increased hole distance the initial angular error that still allows success is reduced to 0.75 degrees, thereby making the direction a more important factor as the length of putt increases.

Target range, m (ft)

4.5 (14.76) 4.0 (13.12) 3.5 (11.48) 3.0 (9.84) 2.5 (8.20)

This figure shows the target range (the distance the ball would reach if uninterrupted) and ‘initial angle’ (angular deviation) when hit that will result in the ball dropping in the cup on a sightly uphill green (of 2-degree incline).5 This shows that for a ball approaching the hole on line (i.e. initial angle = 0º), the target range can be anywhere between 2 and 4 m (6.5 and 13 ft) for it to drop in. If the target range is above 4 m (13 ft) the ball will arrive at the hole too fast to go in and will skip over the hole and carry on rolling. Hit to a fraction under 2 m (6.5 ft), a tolerable angular error of ±1.3 degrees will still see the ball drop.

–2 –1 0 +1 +2 Angular deviation from perfect track (degrees)

Making tracks

a Ball path The track of a ball can be computed for an ideal undulating green.5 In simple terms, the curvature of the ball’s path is related simply to the local slope and to the local ball speed. On a level green the distance travelled is proportional to speed – hitting the ball twice as hard sends it four times as far. 2,5

For a level putt, the target range is proportional to initial ball speed squared.

For a putt across an undulating green, the path of the track taken by the ball can be predicted by taking into account the slope angle and ball speed at each point.

151

What is the best overall pace for putts?

Should you lag your putt to die at the hole?

Given that the putt is such an important aspect of golf, the goal of attaining the smallest number of strokes possible is sometimes compromised when the ball either pulls up a fraction short of the hole, or bounds straight over it as if the hole wasn’t there in the first place. Getting the speed at which the ball is captured by the hole just right can mean the difference between making par, winning a hole, a match, or, more significantly, a professional tournament. Capture speed dynamics are simple: the faster the ball is rolling at the hole, the narrower the hole effectively becomes. This is because it takes a certain amount of time for the ball to fall into the hole (i.e. 0.07 s), and if the ball is rolling too fast and/or hitting the hole off-centre, there is not enough time for the middle of the ball to drop below the top of the cup. For that reason a delivery speed between one and four

revolutions per second has been recommended so that the hole width is effectively maximized and the wobble caused by the slowing ball is moved behind the hole, rather than in front of it.1 In examining the factors that may contribute, given a set of conditions, to the optimal delivery speed of a putt, several assumptions are made. One is the behaviour of the grass at the edge of the hole, which has two effects: under the weight of the ball, the grass at the front edge of the hole will compress, allowing the ball to begin falling sooner - this means that the ball can move a bit faster when it reaches the hole and still fall in; and the grass at the back edge of the hole will undergo deformation the moment the ball strikes it, meaning that energy will be absorbed by the grass, which slows the ball, and implies

d Ball delivery 1.3 cm (0.5 in) wide

3.8 cm (1.5 in) wide

The maximum chance of your ball being captured by the hole is when it arrives at the rim of the cup at topple-in velocity – that being a ball rotating just under 1 revolution per second. At this speed the whole width of the hole becomes available. However, this just-fall-over-the-edge velocity increases the risk of your ball being knocked off line as it slows down.1

6.4 cm (2.5 in) wide Ball delivery speed (7 rev/s-1/0.9 ms-1)

9 cm (3.5 in) wide 10.8 cm (4.25 in) wide

Ball delivery speed (5 rev/s-1 /0.7 ms-1) Ball delivery speed (3 rev/s-1/ 0.4 ms-1) Ball delivery speed (1 rev/s-1/ 0.1 ms-1) Ball delivery speed (